bluuebunny/crossref_metadata_2025 huggingface dataset:
Contribution of PPARα and Ketone Body to Sleep Homeostasis in Mice
Authors: Chikahisa Sachiko , Shimizu Noriyuki , Shiuchi Tetsuya , Sei Hiroyoshi
Published: June 2021

Sleep and energy metabolism have been known to share common regulatory mechanisms. Sleep restriction leads to metabolic disorders such as obesity and diabetes. However, the mechanisms of the relationships between sleep restriction and metabolic disorders have remained elusive. We have recently found that peroxisome proliferator‐activated receptors alpha (PPARα), a transcriptional factors belonging to the nuclear receptor, is involved in the regulation of sleep homeostasis. Chronic treatment of bezafibrate, a PPARs agonist enhanced the slow‐wave activity (SWA) in non‐rapid eye movement (NREM) sleep in mice. In the bezafibrate‐treated mice, plasma concentration of acetoacetate (AcAc) was increased while β‐hydroxybutyrate (BHB) was decreased. Ketogenesis is modulated by the activity of PPARα under the condition of low glucose availability. To investigate the specific effects of ketone bodies on sleep homeostasis, plasma concentration of ketone bodies were measured after sleep deprivation for 6 hours. Sleep deprivation increased plasma ketone bodies (both AcAc and BHB) and increased mRNA expression of PPARα and mitochondrial 3‐hydroxy‐3‐methylglutaryl CoA synthase 2 (Hmgcs2), a rate‐limiting enzymes of ketogenesis, in the hypothalamus and cortex. In addition, central injection of AcAc, but not BHB, increased SWA during NREM sleep and suppressed glutamate release. These results suggest that central PPARα and ketone body metabolism play a significant role in the interaction of lipid metabolism and sleep homeostasis.
Sleep Restriction Delays Suction Blister Skin Barrier Restoration
Authors: Smith Tracey , Wilson Marques , Young Andrew , Montain Scott
Published: June 2021

The suction blister model creates experimental skin wounds and permits evaluation of local immune response and wound healing. This pilot study assessed the effect of sleep restriction on skin barrier recovery after induction of a skin blister. Up to 8 blisters (~30 mm2) were induced via suction on participant's non‐dominant forearm either after 5 nights of adequate sleep (AS, 6.5‐9‐h sleep per night confirmed via activity monitors), after 48‐h of sleep restriction (RS, monitored in laboratory with ~2‐h sleep per night), or after 48‐h of sleep restriction in participants who underwent 72‐h sleep restriction (RS+). Top layer of blisters was removed to reveal up to 8 wounds. Skin barrier recovery was assessed by transepidermal water loss, measured daily until values were within 90% of unbroken skin. ANOVA with Tukey post‐hoc comparison determined significant between‐group differences. Skin barrier recovery was shorter for AS (n = 16, 23±5 years [mean±SD]) compared to RS (n = 10, 20±2 years) and RS+ (n = 10, 21±3 years): 4.2±0.9, 5.1±0.9 and 5.3±0.8 days, respectively (P = 0.008). Skin barrier recovery was not statistically different between RS and RS+. These data support the hypothesis that relatively modest sleep disruption delays wound healing.

The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.
Bufodienolides in the Rat Adrenal Gland
Authors: Darlington Daniel , Gann Donald
Published: June 2021

Intracellular water and electrolyte balance is regulated in large part by Na/K ATPase. Inhibition of this enzyme leads to cellular depolarization, a rise in extracellular K and intracellular Na, cellular swelling, and has been associated with shock, and failure to restore blood volume after hemorrhage. Bufadienolides are a strong inhibitor of Na/K ATPase and have recently been identified in plasma and urine of swine and man. To identify which organs synthesize bufadienolides, various organs from rat were homogenized. Bufadienolides were extracted using 1x volume ethyl acetate/ 4x volume acetonitrile, dried, and extracted by affinity chromatography (DigiFabTM, Fougera Pharmaceuticals INC). Extracts were run on Reverse Phase High Pressure Liquid Chromatography (Beckman Coulter). Chromatographic peaks were identified as Telocinobufagin, marinobufogenin, bufalin, and resibufogenin from testis, adrenal and brain by 1) co‐elution of standards, 2) UV spectrum and 3) mass spectroscopy of collected fractions. These data suggest that bufadienolides, potent inhibitors of Na/K ATPase, are synthesized in testis, adrenal and brain of rat. Supported by the ARMY MRMC and DMRDP.
The effects of two TGF‐beta superfamily ligand trapping agents on the morphology of dystrophic (mdx) Triangularis Sterni (TS) muscle
Authors: Nielsen Cory , Borowy Christopher , Jacinto Kimberly , Potter Ross , Kaminski Carter , Kumar Ravi , Carlson C George
Published: June 2021

The severely dystrophic mdx TS muscle provides a useful template for examining the translational efficacy of various signaling modulators in ameliorating dystrophic pathology. Two critical skeletal muscle modulators are myostatin and TGFβ, which activate the same smad signaling pathway through their respective receptors, ActRIIB and TGFβRII. To independently examine the relative effects of myostatin and TGFβ signaling on dystrophic fiber morphology, we administered either an ActRIIB (RAP‐031, RAP‐435) or a TGFβRII ligand trapping agent (TGFβRII‐Fc) in vivo to mdx mice for 1 month or 3 month periods. There was an increase in fiber and myonuclei density following 1 month treatment with RAP‐031, RAP‐435, or TGFβRII‐Fc. After 3 months treatment with RAP‐435, there was a significant increase in fiber and myonuclei density across all regions of the TS but no effect on Feret's minimal diameter. In addition, 3 month RAP‐435 treated preparations showed a decrease in central nucleation. Histograms of the number of fibers with centrally located nuclei followed a Poisson distribution. This indicates that the probability of a nucleus occupying a central location does not depend upon the presence of other centrally located nuclei and is identical for each myonucleus within a given fiber. Experiments examining the effects of a 3 month treatment with TGFβRII‐Fc are underway. These results indicate that ActRIIB inhibition promotes satellite cell regeneration and fusion into new myotubes and does not increase individual fiber growth in the mdx TS.
Altered Fiber Types in Regenerated Muscle of Fktn‐KO Muscular Dystrophy Mice
Authors: Beedle Aaron , Modi Jill , Melick Garrett , Abousaud Marin , Fortunato Marisa , Foltz Steven
Published: June 2021

Secondary dystroglycanopathies are a class of muscular dystrophy caused by mutations in genes, including fukutin (FKTN), that are important for the glycosylation of alpha‐dystroglycan (aDG). Loss of glycosylation disrupts aDG binding to laminin, causing defects in muscle and nervous tissues. To assess the role of aDG in fiber type specification of regenerating muscle, we compared muscle fiber types 14 days after toxin injury in skeletal muscle‐specific (Myf5, developmental) and whole animal, post‐development‐induced (TAM) models of Fktn deficiency (KO) at equivalent times post‐gene deletion. Embryonic myosin heavy chain‐expressing fibers, an early regeneration marker, were increased in TAM‐Fktn KO mice 14 days after injury, suggesting that aDG disruption may delay muscle differentiation in this model. Oxidative fibers (type 1 and type 2A) were increased after injury in the TAM‐Fktn KO compared to Myf5‐Fktn KO mice. Type 2X fibers were reduced in toxin regenerated muscle compared to vehicle‐treated muscle for all study groups except the Myf5‐Fktn KO mice. Instead, Myf5‐Fktn KO showed a trend towards fewer type 2X fibers on the uninjured side. These data suggest that aDG contributes to skeletal muscle maturation and fiber type specification in a manner that may be timing and/or location dependent.
VLA‐4 Targeted Radiopharmaceuticals for Seeing and Treating Metastatic Melanoma
Authors: Anderson Carolyn , Beaino Wissam , Nedrow Jessie
Published: June 2021

Melanoma is a malignant tumor derived from epidermal melanocytes and is known for its therapeutic resistance, aggressive clinical behavior, and predisposition for late metastasis. Very late antigen 4 (VLA‐4) is a transmembrane non‐covalent heterodimer (also called integrin alpha 4 beta 1) overexpressed in melanoma tumors that plays an important role in tumor growth, angiogenesis and metastasis by promoting adhesion and migration of cancer cells. There has been increasing interest in targeting this receptor for cancer imaging and therapy. Here we evaluated analogs of the high VLA‐4 binding peptidomimetic ligand, LLP2A, for PET‐CT imaging (labeled with Ga‐68; positron emitter, half‐life = 68 min) and targeted radiotherapy (labeled with Lu‐177; beta minus emitter, half‐life = 6.7 d). The DOTA‐PEG4‐LLP2A analog was labeled with Ga‐68 and Lu‐177, and the two agents showed high affinity to VLA‐4 in B16F10 mouse melanoma cells (IC50 = 1.56 nM and Kd = 4.1 nM, respectively). B16F10 subcutaneous tumors in C57/BL6 mice avidly took up the Lu‐177‐labeled agent, with a tumor:blood ratio of 185 at 24 h post‐injection, while the Ga‐68‐labeled analog had a tumor:blood of 6 at 1 h post‐injection. Ga‐68‐DOTA‐PEG4‐LLP2A visualized 1‐2 mm B16F10 metastases in albino C57/BL6 mice by small animal PET/CT. Ga‐68‐DOTA‐PEG4‐LLP2A is ready for translation to humans as a PET imaging agent to determine expression levels of VLA‐4 as a biomarker for aggressive, metastatic disease. Therapy studies with Lu‐177‐DOTA‐PEG4‐LLP2A in B16F10 tumor‐bearing mice are underway.
Sympathetic Neurovascular Regulation During Pregnancy: A Longitudinal Case Study
Authors: Steinback Craig , Usselman Charlotte , Davenport Margie
Published: June 2021

Pregnancy is associated a ~50% increase in blood volume, ~40% increase in cardiac output (Q), offset by a drop in total peripheral resistance (TPR). While limited data indicate a concurrent increase in sympathetic nerve activity (SNA) in normal pregnancy, suggesting reduced transduction of SNA into TPR, longitudinal neurovascular adaptation during gestation remains poorly understood.

We conducted a longitudinal assessment of SNA and TPR in a 36 year old woman during her second pregnancy. Measures were made on 2 occasions in the month prior to conception, 4 occasions during pregnancy (9, 24, 30, and 38 wks gestation) and again 10 wks postpartum. Mean arterial pressure (MAP; Finometer) and Q (ModelFlow) were measured and used to calculate TPR. SNA was measured using microneurography (peroneal nerve).

There was a gestationally dependent increase in SNA burst frequency (r2=0.970, P<0.01) and incidence (r2=0.977, P<0.01); frequency (24 bpm to 59 bpm) and incidence (34 b/100hb to 65 b/100hb) increased 145% and 89% respectively by 38 wks compared to early follicular values. However, transduction (TPR/SNA Burst Frequency) decreased throughout pregnancy (r2=0.952, P<0.05; 0.80 au to 0.21 au). By 10 wks postpartum, SNA (24 bpm; 28 b/100hb) had returned to pre‐pregnant values whereas transduction (0.44au) remained lower.

These longitudinal data highlight the progressive sympoathoexcitation during pregnancy which is offset by a concurrent reduction in neurovascular transduction. Sympathetic hyperactivity reverses early in the post‐partum whereas transduction remains decreased. Funded by WCHRI, NSERC, HPF
Differential Effects from Pharmacological and Electrical Stimulation of Rabbit Cardiac Ganglia
Authors: Brack Kieran
Published: June 2021

Cardiac autonomic innervation is complex due to the presence of an independent network of intrinsic cardiac ganglia, which are capable of differentially modulating cardiac function. Cardiac effects from these ganglia are studied using pharmacological or electrical stimulation and this was investigated in the current study. Langendorff perfused NZW rabbit hearts (2.5‐3kg) were used and ganglionic effects from left and right neuronal complexes (RNC) studied. Nicotine was used for pharmacological activation (0.1mg/10ul) and compared to electrical stimulation (20‐50Hz, 500‐700uA). Heart rate (HR) and atrioventricular conduction (AVC) was measured during control, muscarinic (atropine, 0.1uM), beta‐receptor (metoprolol, 1.8uM) and nicotinic (hexamthonium, 0.5uM) receptor blockade. Nicotine elicited mixed HR responses i.e. bradycardia alone, tachycardia alone and/or a mixed brady/tachycardia at each site. At the LNC, there was a smaller bradycardia (147.9±5.0 ‐ 142.2±5.6 bpm) but larger tachycardia (208.1±6.8 bpm) vs. the RNC (146.1±4.5, 131.5±5.4 [brady], 191.3±8.0 [tachy] bpm). Nicotine elicited AVC prolongation and/or shortening at each site. AVC prolongation was largest at the RNC (122.4±3.2 ‐ 129.5±3.6 ms) vs. the LNC (122.9±4.1 ‐ 126.2±4.3 ms). AVC shortening was indifferent. Only bradycardia and AVC prolongation was elicited by electrical stimulation. Responses were largest at the RNC. Bradycardia/AVC prolongation was blocked by atropine. Tachycardia/AVC shortening was blocked by metoprolol. Hexamthonium blocked all responses. These are the first data to show functional effects from ganglionic plexus stimulation in the rabbit with different responses from pharmacological vs. electrical stimulation.
Long‐Term Exposure of Particulate Matter to Lean and Obese Mice Leads to Cardiac Dysfunction Through Alterations in Beta‐Adrenergic Signaling
Authors: Gorr Matthew , Eichenseer Clayton , Youtz Dane , Nelin Timothy , Wold Loren
Published: June 2021

Exposure to the particulate matter (PM) component of air pollution causes significant effects on cardiovascular health, specifically exposure to PM less than 2.5 µm in diameter (PM2.5). Numerous studies have linked increases in PM2.5 levels with cardiovascular events and mortality. In the present study, we exposed adult lean and obese mice to ambient PM2.5 at relevant concentrations or filtered air (FA) and examined cardiovascular function using echocardiography at regular intervals. At 5 and 9 months, we sacrificed the animals to measure cardiomyocyte contractility and calcium transients, in addition to protein analysis. After 5 months, obese mice exposed to PM2.5 had reduced fractional shortening (%FS) compared to FA mice, an effect that was not apparent in the lean mice. At 9 months, lean mice had reduced %FS and decreased pulmonary output. Analysis of cardiomyocytes isolated from these mice recapitulated the in vivo phenotype, as cells from the PM2.5 group had reduced contractile parameters and lengthened calcium reuptake compared to FA exposed mice. PM2.5 cells treated with isoproterenol (ISO) from both lean and obese groups had an exacerbated contractile response compared with ISO treated cells from the FA groups. Molecular analyses of lean mice exposed for 9 months revealed that PM2.5‐exposed mice had increased phospholamban protein and increased troponin I phosphorylation. We conclude that long‐term exposure to PM2.5 leads to the reduction of cardiac function by altering contractile proteins, possibly through compensatory alterations to beta‐adrenergic signaling.
Rac1 as a Potential Candidate for Improved Insulin Sensitivity Following Exercise
Authors: Sheikh Shabnam , Yamazaki Katrina
Published: June 2021

It has long been known that physical exercise alleviates insulin resistance in diabetes. While several mechanisms of action have been explored, a clear signaling pathway has yet to be determined. One possible candidate for involvement is Rac1, a rho GTPase. Downstream of PI3K, Rac1 is involved in actin remodeling in the context of GLUT4 translocation and is activated in response to both insulin and exercise. Although Rac1 is active during exercise, the duration of activation following exercise is yet to be determined and may be critical in the post‐exercise improvements in insulin stimulated glucose uptake. The goal of my project is two‐fold. First, I plan to investigate the duration of Rac1 activation following exercise. Secondly, I plan to investigate Rac1′s role in the insulin/exercise signaling pathway by examining potential upstream and downstream proteins. Experiments will be conducted in vitro, using differentiated C2C12 murine skeletal muscle cells and electrical stimulation will be used in place of exercise to stimulate contraction. Cells will be cultured in normal media or in glucolipotoxicity media to mimic diabetes. Following electrical stimulation, active Rac1 levels will be measured at varying time points to determine length of Rac1 activation. In addition, to map out the Rac1 signaling pathway, various proteins will be blocked and downstream activity will be measured to determine the pathway.
Water Intake and Hyperinsulinemia in a National Sample of U.S. Adults: An Analysis of NHANES Data
Authors: Johnson Evan , Cardenas Victor , Kavouras Stavros
Published: June 2021

The purpose of this investigation was to investigate whether water intake was associated with hyperinsulinemia in a probability sample of US adults who were free of diabetes. We examined data on 1,943 participants from the 2009‐2010 National Health and Nutrition Examination Survey to assess if the following independent variables (geometric mean ± SE); urine osmolality (Uosmo, 536 ± 12 mmol/kg), urine flow rate (UFR, 1.28 ± 0.03 ml/min), water consumed as a beverage (Wbev, 184 ± 15 ml), or total water intake from food and beverages (TWI, 2,664 ± 35 ml) predicted fasting plasma insulin (FPI), fasting plasma glucose (FPG), or the homeostasis model of insulin resistance (HOMA; calculated from FPG and FPI). Relationships were evaluated via multiple linear regression analysis after controlling for metabolic equivalent expenditure, waist circumference (WC), and education level. The data revealed that HOMA was negatively associated with UFR (β =‐0.059, p = 0.030), Wbev (β =‐0.018, p = 0.005), and TWI (β =‐0.085, p = 0.040). Waist circumference appeared to negatively confound the effect of these variables on hyperinsulinemia. Only Wbev was a significant predictor of FPI, (β =‐0.260, p = 0.020). No predictors were significantly related to FPG. Overall, the amount of water consumed, as a beverage, and within all foods and beverages, along with the rate of urine produced was related to insulin resistance in people without diabetes. WC confounding suggested increased water intake in individuals with larger WC may represent early stages of diabetes. Thus, higher TWI seems to provide a protective effect against hyperinsulinemia and the development of diabetes.
Post‐weaning western style diet leads to increased activity of Complex IV of non‐human primates when exposed to western style diet in utero.
Authors: Macrorie Sarah , Wilcox Margaret , Hetrick Byron , McCurdy Carrie
Published: June 2021

Adult offspring of insulin resistant mothers show increased susceptibility to type 2 diabetes and obesity. Previous studies in this population have found reduced mitochondrial function and decreased lipid oxidation in skeletal muscle consistent with insulin resistance. It is not known how maternal diet affects functioning of the individual electron transport chain complexes. We were specifically interested in investigating whether exposure to maternal western style diet (WSD), or post‐weaning (PW) exposure to WSD, would impact functioning of Complex IV (CIV) when compared across treatment groups. Gastrocnemius muscle homogenates taken from 1 year old juvenile Japanese Macaque of dams exposed either to a control (CTR) or WSD prenatal (PN), and a CTR or WSD PW diet, were assayed for activity in Cytochrome C oxidation, reporting on the activity of CIV in these tissues. We hypothesized that in‐utero exposure to maternal WSD would lead to functional changes in complex IV of the electron transport chain. Our results showed no direct effect of maternal diet on CIV activity, but an increase in CIV activity when prenatally exposed offspring were fed a PW WSD. When analyzed by sex, males showed an increase in CIV activity when exposed to PN WSD, while females showed an increase in CIV with exposure to PW WSD, regardless of PN exposure. Experiments assessing citrate synthase activity shows no change with exposure to PN WSD, indicating that there is no increase in mitochondrial number. Taken together, these data show that while there is no increase in mitochondrial number, there is an increase in CIV activity with exposure to both PN and PW WSD in males and females, and increased activity in females regardless of PN exposure.
The Effect of Dobutamine on Susceptibility to Ischemia‐Induced Ventricular Fibrillation in the Isolated Rat Heart
Authors: Clements‐Jewery Hugh , Haines Jeremiah
Published: June 2021

Sudden cardiac death due to ventricular fibrillation (VF) continues to be a major cause of mortality, but the triggers of VF in ischemia remain poorly understood. Our hypothesis is that VF is triggered in myocardial ischemia as a result of ATP depletion, which causes ionic imbalance and electrical dysfunction that creates an arrhythmogenic substrate. The purpose of this study was to test this hypothesis by determining the effect of increasing cardiac ATP consumption on susceptibility to VF using a classical inotrope, dobutamine.

Isolated rat hearts (n=12 per group) were perfused in the Langendorff mode with modified Krebs containing 3 mM K+. Dobutamine or vehicle was locally infused in a randomized and blinded manner to achieve a concentration of dobutamine of 3µM. After a further 15 min, regional ischemia was induced by coronary artery occlusion and maintained for 30 min. VF was determined from the ECG, and cardiac function was evaluated using an intraventricular balloon.

Dobutamine increased heart rate and left ventricular developed pressure compared to controls as expected. The incidence of VF (75% vs 67%; P=NS) and time to onset of VF (892±68s vs 730±80s; P=NS) were similar in control and dobutamine groups respectively. Dobutamine reduced ischemic contracture, with end diastolic pressure 36±6 vs 15±3 mmHg after 25 min ischemia in control and dobutamine groups respectively (P<0.05). Thus, although β1 stimulation by dobutamine increased cardiac work, it did not increase susceptibility to ischemic VF.
Exposure to Diesel Exhaust Particles Drive Expansion of Cardiac Ischemia‐Reperfusion Injury via Interleukin‐6 Trans‐Signaling in Male Sprague‐Dawley Rats
Authors: Holland Nathan , Harris Gregory , Lust Robert , Wingard Christopher
Published: June 2021

Exposure to particulate matter has been strongly associated with deleterious impacts on cardiovascular health and function; however, the mechanisms that underlie this association are largely unknown. We have hypothesized that exposure to particulate matter drives cardiovascular expansion of cardiac ischemia‐reperfusion injury (I/R) via a novel mechanism known as IL‐6 trans‐signaling (IL‐6TS) which promotes a proinflammatory state, increasing susceptibility to inducible injury. To test our hypothesis we exposed male Sprague‐Dawley (SD) rats to an intratracheal (IT) bolus of 200 µg of diesel exhaust particles (DEP) or saline control. To examine inducible injury 24, 48, and 72 hours following IT instillation rats underwent 15 minutes of coronary artery ligation followed by 2 hours of reperfusion. 24 hours after IT exposure to DEP I/R injury was expanded versus control. Likewise, 48 hour following IT instillation I/R injury was elevated versus control, but was reduced from 24 hours. At 72 hours I/R injury was once again elevated to a similar degree as 24 hours. To implicate IL‐6TS in the exacerbation of I/R injury ELISAs for elements of IL‐6TS were performed on serum collected at 24 hours from SD rats exposed to IT DEP; resulting in increases of circulating IL‐6, soluble IL‐6 receptor, and a concomitant decrease in soluble glycoprotein 130, the endogenous antagonist for IL‐6TS. We conclude that exposure to DEP results in a proinflammatory state via IL‐6TS that primes the cardiovascular system for expansion of I/R injury. Funding support in part by Philip Morris International and NIEHS U19 ES019525.
Alterations in Mitochondrial Morphology with Age‐Associated Estrogen Deficiency and Ischemia‐Reperfusion Injury
Authors: Aurigemma Nicole , Garvin Alexandra , Korzick Donna
Published: June 2021

Acute myocardial infarction is the leading cause of death in post‐menopausal women. While age‐associated changes in mitochondrial morphology and dynamics are known to contribute to ischemia reperfusion (I/R) injury in males, there is limited research using physiologically‐relevant models of female aging. Using a novel model to mimic human menopausal estrogen (E2) deficiency, we determined the effects of age and I/R injury on mitochondrial morphology. F344 female rats ovariectomized (OVX) at 15 mo and studied at 24 mo (MO) vs adult (6 mo) were subjected to coronary artery ligation (CAL) with 31 min I and 24 hr or 7 days R. Left ventricular tissue was imaged by transmission electron microscopy. With I/R injury, mean mitochondrial area decreased (20%) in MO and increased (80%) in adult relative to sham, suggesting phenotypes of fission and fusion, respectively with 24 hr R. Further, ~70% of total mitochondria from MO with 24 hr R had areas less than 0.4 μm2 while retaining an increased density. Compared to adult sham, mean mitochondrial area in aged OVX with 7 day R increased 12% in conjunction with increased prevalence of matrix translucency and cristae disruption indicating large, dysfunctional mitochondria. Increased mitochondrial area in aged OVX at 7 days R may also point to compensatory mechanisms to mediate loss of functioning mitochondria. While implications of mitochondrial fission/fusion balance are incompletely understood, our data suggest that with E2 deficiency and I/R injury, fission may be the predominant mechanism in the aged female heart.
Effects of Myocardial Infarction on Cardiac Function and on Exercise Capacity in Obese Mice
Authors: Conti Filipe , Sartori Michelle , Santos Fernando , Dias Danielle , Salemi Vera , Irigoyen Maria , De Angelis Kátia
Published: June 2021

This study was designed to evaluate the effects of myocardial infarction on cardiac function and exercise capacity in obese mice. Female wild type and ob/ob mice (10 weeks) were randomized into (n=6): Control group (C), Obese group (O) and Obese Myocardial Infarction group (OMI). Coronary artery occlusion was performed on 10 week old. Cardiac morphology and function were assessed by echocardiography 24‐48hs after myocardial infarction. The maximal exercise test was performed on a treadmill. The body weight was higher in obese groups (O: 50±0.5; IMO: 54±2 g) in relation to C group (20±0.2 g). The eject fraction was markedly reduced in OMI group (37.24±0.06%) than C (55.20±0.05%) and O groups (66.09±0.02%). Left ventricular mass corrected by body weight was reduced in obese groups (O: 1.99±0.1; IMO: 1.06±0.09 mg/g) when compared to C group (4.11±0.45 mg/g). The exercise capacity, verified by the running time, showed a reduction in O group (7.6±0.4 min) when compared to C group (16.0±0.5 min). The OMI group showed an additional decrease in left ventricular mass and exercise capacity (2.9±0.5 min) in relation to O group. We observed a positive correlation between eject fraction and exercise capacity (r=0.87, p<0.0001) when analyzed only obese groups. In conclusion, the myocardial infarction promoted cardiac dysfunction in ob/ob mice, which was correlated with an impairment on exercise capacity. These data suggest that maximal exercise test can be used as a tool to identify cardiac dysfunction and prognosis in obese subjects after an ischemic event.
Abnormal Regulation of Placental Growth Factor in Skeletal Muscle of Western‐Diet Fed Mice
Authors: Silva Asitha , Lloyd Pamela
Published: June 2021

Diabetics often develop peripheral artery disease (PAD). Arteriogenesis can preserve blood flow distal to occlusion and limit skeletal muscle ischemia in PAD, but is reduced in diabetics by an undefined mechanism. Placental growth factor (PLGF, a VEGF family protein) is a key arteriogenic factor. Therefore, we hypothesized that skeletal muscle PLGF expression and/or regulation could be abnormal in diabetic PAD. We tested this hypothesis in 3 mouse models with varying degrees of metabolic dysfunction: Western diet (WD) fed C57BL/6J (C57‐WD; n=52), control diet (CD) fed ApoE‐/‐ (ApoE‐CD; n=38) and WD fed ApoE‐/‐ (ApoE‐WD; n=32). CD fed C57BL/6J (C57‐CD; n=48) served as controls. Males and females were studied. Metabolic status was characterized by measuring relevant plasma values. After 6 mo on the diets, skeletal muscle PLGF was assessed under baseline conditions (n=58) and 3‐28 d post‐femoral artery occlusion (n=112). VEGF‐A was measured for comparison. Baseline skeletal muscle PLGF protein was decreased in all WD fed groups (p<0.005), with no effect of gender or strain. Regression analysis of PLGF vs metabolic parameters revealed modest correlation with plasma insulin (r2=0.44, p<0.0001). PLGF was sharply elevated in skeletal muscle of C57‐CD mice after femoral occlusion, peaking ~10 d post‐occlusion. This response was decreased and delayed in C57‐WD mice (p<0.05). Even more strikingly, upregulation of PLGF by occlusion was completely abolished in ApoE‐CD and ApoE‐WD mice. We conclude that in skeletal muscle, Western diet‐induced metabolic dysfunction both reduces baseline levels of PLGF and inhibits its upregulation by the physiological stimulus of occlusion. This phenomenon may contribute to the poor arteriogenic response in diabetes. Support: R01 HL084494 (PL).
NK Cell Mediated Cytotoxicity: A Potential Mechanism of Endothelial Progenitor Cell Dysfunction in the SS Rat
Authors: Exner Eric , Abel Alex , Parker Sarah , Malarkannan Subramaniam , Greene Andrew
Published: June 2021

Endothelial progenitor cells (EPCs) are adult stem cells with roles in angiogenesis and endothelial function. Studies suggest that autologous stem cell therapy using EPCs is therapeutic in microvascular disease; however, results from clinical trials have been mixed. EPCs from diseased/aging hosts show decreases in number and function that could compromise their therapeutic efficacy, and this is likely to be masking the potential of EPC based therapy. The objective of this study was to determine the mechanism of EPC dysfunction in an animal model of salt‐sensitive hypertension and impaired angiogenesis. In the SS/MCWi (SS) rat, EPC competency and longevity are impaired in vivo but rescued in vitro. We have found that SS EPCs express higher levels of natural killer cell receptor 2B4 (2B4) on their cell membrane than EPCs from healthy genetic controls, consomic SS‐13BN rats. 2B4 has been shown to induce NK cell mediated cytotoxicity when overexpressed on target cells. We isolated EPCs and NK cells from SS and SS‐13BN rats and measured NK cell mediated cytotoxicity with an LDH release assay. SS EPCs were more susceptible than SS‐13BN EPCs to destruction by both sets of NK cells. SS NK cells were more potent killers of EPCs than SS‐13BN NK cells, suggesting that NK cell function is altered in the SS rat. We hypothesize that increased membrane expression of 2B4 by SS EPCs leads to destruction by NK cells in vivo, which compromises their ability to induce angiogenesis. (NHLBI HL‐082798)
Hypocapnic Hypoxia Silences the Retrotrapezoid Nucleus (RTN)
Authors: Basting Tyler , Burke Peter , Stornetta Daniel , Stornetta Ruth , Guyenet Patrice
Published: June 2021

Rationale and objectives

In conscious mammals, hypoxia produces respiratory alkalosis which is assumed to silence central respiratory chemoreceptors (CRCs). We tested this theory by examining how hypoxia changes the activity of the RTN, a likely CRC and chemoreflex integrator.

Methods

RTN and nearby C1 neurons were bilaterally transduced with archaerhodopsin using a lentiviral vector (PRSx8‐ArchT‐EYFP‐LVV). We first showed that RTN neurons were silenced by green light in anesthetized rats. We then recorded the effect of RTN inhibition (10s) on breathing (fR, VT), BP, EEG and neck EMG in conscious rats exposed to normoxia, hypocapnic hypoxia (12 or 15% O2), isocapnic hypoxia (12% O2 + 3% CO2) or hypoxia in presence of acetazolamide (ACTZ). Arterial PO2, PCO2, pH and HCO3 were measured in each condition.

Results

In normoxia RTN inhibition reduced breathing equally during non‐REM sleep and quiet wake and BP was unchanged. ΔfR was largest in normoxia, reduced in 15% O2, nul in 12% O2 and back to control (normoxia level) in normocapnic hypoxia.ΔVT followed the same trend. RTN inhibition caused much larger fR and VT reductions in ACTZ‐treated rats. Overall the bradypnea caused by RTN inhibition was linearly correlated with pHa (p < 0.0002). Above pHa 7.5, no fR change was elicited.

Conclusions

RTN neurons regulate breathing equally during sleep and wake. RTN neurons are the first putative CRCs demonstrably silenced by hypocapnic hypoxia in conscious mammals. RTN is silent above pHa 7.5 and increasingly active below this value. Under hypocapnic hypoxia carotid body stimulation drives breathing via pathways that bypass RTN. ACTZ increases breathing by activating RTN. Funding: HL074011 (PGG), 5T32HL007284‐38 (TMB).
Sustained Hypoxic Pulmonary Hypertension and Systemic Vascular Dysfunction in High‐Altitude Dwellers Prone to Re‐Entry High Altitude Pulmonary Edema, Improvement by Anti‐Oxidants
Authors: Cerny David , Rexhaj Emrush , Bouillet Elisa , Soria Rodrigo , Meister Théo , Villena Mercedes , Sartori Claudio , Allemann Yves , Scherrer Urs , Rimoldi Stefano
Published: June 2021

Re‐entry high altitude pulmonary edema (HAPE) is a live‐threatening problem that occurs on return from low altitude in otherwise healthy high‐altitude dwellers. The underlying mechanism is poorly understood. Circumstantial data suggest that pulmonary vascular dysfunction facilitating hypoxic pulmonary vasoconstriction plays a role. There is increasing evidence that at in high altitude dwellers, pulmonary vascular dysfunction is often associated with alterations of the systemic circulation related to altered redox regulation. We speculated that re‐entry HAPE prone subjects display sustained pulmonary and systemic vascular dysfunction related to increased oxidative stress.

We therefore measured systolic pulmonary artery pressure (PAP, echocardiography), flow mediated dilation of the brachial artery and carotid intima‐media thickness (IMT) in re‐entry HAPE prone subjects and controls living at 3600 m. The main new findings were 2‐fold: 1) PAP was significantly higher in re‐entry‐HAPE prone than control subjects (38±2 vs. 24±1 mm Hg, p<0.001, X±SE) and this pulmonary vascular dysfunction was associated with systemic vascular alterations, as evidenced by increased IMT (485±21 vs. 404±10µm, p=0.002) and decreased FMD (5.1±0.6 vs. 9.7±0.8%, p<0.001). 2) Vit. C administration normalized FMD (Vit C 3 g i.v., 9.2±1.3% p=NS vs. controls) and decreased PAP (Vit C 1g/d for 30 d, 31 ± 1 vs. 38±2 mm Hg, p=0.04) in re‐entry HAPE prone subjects. Here we show for the first time that re‐entry HAPE prone high‐altitude dwellers display generalized vascular dysfunction that is related to altered redox‐regulation.
Guanylate cyclase, potassium channels and eNOS are involved in TERPY effect in resistance vessels of SHR
Authors: Potje Simone , Troiano Jéssica , Graton Murilo , da Silva Roberto , Bendhack Lusiane , Antoniali Cristina
Published: June 2021

The hypotensive effect of the nitric oxide donor ([RU(TERPY)(BDQ)NO]3+) (TERPY) is slowly and long lasting in spontaneously hypertensive rats (SHR). Endothelium improves the relaxant effect of TERPY in SHR aorta. TERPY effect in resistance vessel of SHR was not studied yet. The aim of this study was evaluate the mechanism of TERPY effect in 2nd or 3rd branches of mesentery artery of SHR. Rings were pre‐contract with Phenylephrine and TERPY curves (0,1nmol/L to 100mmol/L) were performed using DMT‐myograf system (PowerLab 8/35). The presence of the endothelium was verified by acetylcholine effect (80%). Rings were pre‐incubated with ODQ (1 mmol/L), TEA (1 mmol/L), L‐NAME (100 mmol/L), ODQ+TEA or ODQ+TEA+L‐NAME. Endothelium improves TERPY´s effect. In rings with endothelium, L‐NAME reduced the potency of TERPY, ODQ or TEA decreased the potency and maximun effect (Emax) of TERPY. ODQ+TEA+L‐NAME reduced Emax, but did not abolish the TERPY effect. In rings without endothelium, both ODQ or TEA decreased the potency and Emax of TERPY and ODQ+TEA abolished TERPY effect. In conclusion, TERPY´s effect in resistance vessel of SHR is dependent of guanylate cyclase (GC), potassium (K+) channel and NOS activation.
Muscle Reflex Effects on the Autonomic Hemodynamic Response to Passive Leg Movement in Older Individuals
Authors: Weavil Joshua , Sidhu Simranjit , Venturelli Massimo , Rossman Matthew , Jessop Jake , Richardson Russell , Bledsoe Amber , Amann Markus
Published: June 2021

Utilizing passive leg movement (PLM), it has recently been documented that leg afferent‐mediated muscle reflexes (predominantly group III) play a critical role in central (cardiac output, Q; stroke volume, SV; heart rate, HR) and peripheral (leg blood flow, LBF) hemodynamic responses in young individuals. The purpose of this study was to examine the impact of age on the role of the muscle reflex in PLM‐induced hemodynamics. Eight men (67 ± 9 yrs) underwent 2 min of passive knee‐extension before (CON) and after partial blockade of lower limb muscle afferents via lumbar intrathecal fentanyl (FENT). Q (plethysmography), leg perfusion pressure (PP), and LBF (Doppler ultrasound) were measured continuously. Leg vascular conductance (LVC) was calculated as LBF/PP. All variables, assessed at baseline, were significantly affected by PLM. The changes in peak values were similar between CON and FENT for Q (~20% increase; P = 0.11), HR (~15% increase; P = 0.42), SV (~18% increase; P = 0.15), and PP (~7% decrease; P = 0.68). However, as FENT resulted in a greater increase in LBF (266 ± 51% vs. 139 ± 21%; P < 0.05), LVC was also greater (288 ± 51% vs. 155 ± 18%; P < 0.05). These findings are in contrast to prior observations in young individuals in whom, compared to CON, FENT during PLM caused a significant decrease in Q (34% vs. 22%), LBF (295% vs. 210%), and LVC (322% vs. 231%). These findings imply an age‐related shift in the role of the mechanoreceptor‐mediated muscle reflex in regulating central and peripheral hemodynamics. Specifically, group III afferents transition from a facilitating effect on central and peripheral hemodynamics during PLM in the young to having no influence on Q and evidence of restraining LBF and LVC in the old.
Acute Ascorbic Acid Ingestion Does Not Blunt Sympathetically‐Mediated Vasoconstriction During Handgrip Exercise in Older Adults
Authors: Richards Jennifer , Hearon Christopher , Racine Matthew , Luckasen Gary , Larson Dennis , Dinenno Frank
Published: June 2021

The normal ability of contracting skeletal muscle to blunt sympathetic vasoconstriction is impaired in older adults, potentially contributing to the age‐associated impairment in skeletal muscle blood flow during exercise. Acute ingestion of 2g of ascorbic acid (AA) improves forearm blood flow (FBF) during moderate intensity handgrip exercise in older adults. We tested the hypothesis that acute AA ingestion improves the ability to blunt a sympathetically‐mediated vasoconstrictor stimulus during handgrip exercise (15% maximal voluntary contraction: MVC) in 10 older (63±2 years) adults. FBF was measured (Doppler ultrasound) and vasoconstriction was calculated (%Δ forearm vascular conductance [FVC]) in response to reflex sympathetic activation achieved via 2 minutes of ‐40mmHg lower body negative pressure (LBNP) at rest and during steady‐state handgrip exercise prior to and 2h post ingestion of AA. Compared to control, AA increased FBF during exercise (185±15 vs. 212±19 ml/min P<0.05) however there was no change in the amount of vasoconstriction to LBNP at rest (ΔFVC = ‐16±2 vs. ‐16±2%) or during exercise (ΔFVC= ‐12±2 vs. ‐11±4 %). We conclude that acute oral AA is capable of improving FBF during handgrip exercise in healthy older adults but does not improve the ability to blunt sympathetically‐mediated vasoconstriction.

Supported by HL095573
Do ATP and Hydrogen Peroxide Cause Sympatholysis in Rat Soleus Feed Arteries?
Authors: Heckle Tanner , Jasperse Jeffrey
Published: June 2021

Arteries and arterioles constrict less to sympathetic stimulation in contracting compared to resting skeletal muscle (sympatholysis). There is some uncertainty regarding the specific agents causing sympatholysis. We have shown that acidosis, but not shear stress, potassium, or adenosine, is sympatholytic in feed arteries from the predominantly slow twitch soleus muscle. Interstitial fluid concentrations of both adenosine triphosphate (ATP) and hydrogen peroxide (H2O2) increase in contracting skeletal muscle, and we hypothesized that ATP and H2O2 are sympatholytic. Soleus feed arteries (n = 6 per group) were isolated from male Sprague‐Dawley rats and cannulated on two glass micropipettes for in vitro videomicroscopy. We measured the constriction response to the α‐1 adrenergic receptor agonist phenylephrine (PE; 10‐9 M to 10‐4 M, 0.5 log increments) in the presence of varying physiological levels of ATP (0 uM, 1 uM, 10 uM, and 100 uM) and H2O2 (0 uM, 1 uM, 10 uM, and 100 uM). Our data indicate no significant difference in PE‐induced constriction between levels of ATP (maximum constriction 64.1±10.4 % vs. 74.4±8.1 %, 68.9±8.7 %, and 66.1±11.4 %) or H2O2 (maximum constriction 76.9±9.2 % vs. 77.5±5.7 %, 79.7±1.8 %, and 76.5±8.0 %). We conclude that neither ATP nor H2O2 independently cause sympatholysis of α‐1 adrenergic receptors in rat soleus feed arteries.
Cardiovascular Risk Related to Body Fat and Physical Activity in Young Girls
Authors: Bea Jennifer , Lee Vinson , Blew Robert , Funk Janet , Going Scott
Published: June 2021

Adiposity has been associated with cardiovascular (CVD) risk factors in children, but whether moderate to vigorous physical activity (MVPA) affects the association remains unclear.

PURPOSE

To determine if MVPA modifies associations between total body fat (TBF) and CVD risk biomarkers of C‐reactive protein (CRP); total (TC), LDL, and HDL cholesterol; triglycerides (TG), and glucose in girls aged 9‐12 years (N=95).

METHODS

Fasting serum CRP was measured by high‐sensitivity nephelometric bead‐based immunoassay; glucose and lipids were measured by clinical laboratory. Dual energy X‐ray absorptiometry estimated TBF. MVPA was assessed by the Past Year Physical Activity Questionnaire. Maturity offset was computed using age and anthropometric measures according to the Mirwald equation.

RESULTS

Mean age and maturity offset were 11.1 ± 1.1yrs and ‐1.83 ± 0.86yrs, respectively. Average TBF was 16.7 kg ± 11.0kg, while %TBF was 33.0 ± 10.6%. Mean MVPA was 45.8 ± 68.2 minutes/day. After controlling for maturity offset in linear regression models, %TBF was positively associated with CRP (β= 0.60, P<0.001), glucose (β=0.24, P=0.02), TC (β=0.29, P<0.01), TG (β=0.31, P<0.01), and LDL (β=0.43, P<0.001). HDL cholesterol was inversely associated with %TBF (β= ‐0.39, P<0.001). When stratified by adequate (蠅60min/d, N=21) versus inadequate MVPA (N=74), %TBF remained significantly associated with all CVD risk biomarkers (P蠄0.05) among those with adequate MVPA, with the exception of glucose.

CONCLUSION

Physical activity may help mediate the effects of body fat on glucose, but it did not attenuate the relationship between body fat and most cardiovascular risk factors among the girls.

Supported by NIH HD074565
Effect of Sit‐Stand Workstations on Metabolic Risk in Sedentary Workers: A Randomized Controlled Trial
Authors: Carpenter Katie , Feltes Linda , Vuong Brenna , Kalbes Ashley , Koepp Gabriel , Dutta Nirjhar , Levine James , Pereira Mark
Published: June 2021

Background

Sedentary time has been shown to have deleterious effects on health. Today's workforce spends most of the day sitting. The objective of this study was to evaluate the effect of workplace interventions to decrease sedentary time on cardiometabolic risk factors.

Methods

Sedentary office workers (n=127; ages 22‐64; BMI=28.5±6.1 kg/m2) were recruited from three Minnesota employers and randomized to one of four intervention groups for 6 months: 1) Control, 2) Move (蠅30 min of light activity during the workday), 3) Stand (standing 蠅50% of the workday using a sit‐stand workstation), or 4) Stand+Move (combined Stand and Move). A 'metabolic risk score' (MRS) was calculated at baseline and 6 months using the following cardiometabolic risk factors: blood pressure, fasting blood glucose, log of fasting triglycerides, and HDL‐cholesterol. A z‐score was computed for each risk factor for each subject [(subject value – sample mean)/sample SD]. The MRS was derived by summing the z‐scores (HDL‐z subtracted).

Results

There was a significant intervention effect on MRS (p<.01). A seasonal time trend was observed, with MRS increasing significantly in Control and Move groups (p<.001), but not for the Stand and Stand+Move. Results (mean±se) are shown in Figure 1.

Conclusions

Sit‐stand workstations combined with an intervention to increase light physical activity at work may be an effective tool to improve cardiometabolic risk.

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Voluntary exercise training attenuates the enhanced sympathetic responses to muscle mechanoreflex activation in spontaneously hypertensive rats
Authors: Mizuno Masaki , Iwamoto Gary , Vongpatanasin Wanpen , Mitchell Jere , Smith Scott
Published: June 2021

Exercise training has beneficial effects on cardiovascular diseases such as hypertension. However, the underlying mechanisms remain to be elucidated. The purpose of this study was to examine whether regular exercise reduces abnormally exaggerated skeletal muscle mechanoreflex function in hypertension. Changes in renal sympathetic nerve activity (RSNA) and mean arterial pressure (MAP) to stimulation of the muscle mechanoreflex were assessed in untrained normotensive Wistar‐Kyoto rats (WKYUT; n = 6), exercise trained WKY (WKYET; n = 7; housed in cage with running wheel for 3 months), untrained spontaneously hypertensive rats (SHRUT; n = 3) and exercise trained SHR (SHRET; n = 7). There was no difference between WKYUT and WKYET in RSNA (40±11 vs. 47±11 %, respectively) and MAP (7.5±4.0 vs. 8.0±4.2 mmHg, respectively) responses to stimulating the mechanoreflex by passively stretching hindlimb muscles. Voluntary wheel running (3 months) significantly attenuated sympathetic responses to mechanoreflex stimulation in SHRET compared with SHRUT (35±12 vs. 113±22 %, respectively, P<0.01). A similar MAP response profile was likewise produced (14±3 vs. 33±22 mmHg, respectively). In conclusion, our data provide the first direct evidence that voluntary exercise ameliorates abnormal mechanoreflex overactivity in hypertension. Supported by NIH HL‐088422 and HL‐113738
Leptin Regulates Synaptic Activity of Brown Adipose Tissue‐Related Pre‐Sympathetic Neurons in the Paraventricular Nucleus of the Mice
Authors: Jiang Yanyan , Munzberg Heike , Derbenev Andrei , Zsombok Andrea
Published: June 2021

Brown adipose tissue (BAT) thermogenesis is critical for maintaining body temperature and thus energy expenditure and it is regulated by the sympathetic nervous system. Recent evidence demonstrated the involvement of leptin in the regulation of the sympathetic outflow to the BAT; however, the underlying cellular mechanisms are poorly understood. In this study, we identified BAT‐related neurons in the paraventricular nucleus of hypothalamus (PVN) of mice (BAT‐PVN) by inoculating BAT with pseudorabies virus 152. Whole‐cell patch‐clamp recordings were performed to test the hypothesis that leptin regulates the synaptic activity of pre‐sympathetic BAT‐PVN neurons. The majority of BAT‐PVN neurons responded to leptin application. Leptin (300 nM) caused an increase of spontaneous excitatory post‐synaptic current (sEPSC) frequency in a subset (40%) of BAT‐PVN neurons, whereas sEPSC frequency was decreased in other subset of BAT‐PVN neurons (30%). This effect was observed without alteration of the amplitude. On the other hand, the frequency of spontaneous inhibitory post‐synaptic currents (sIPSC) was decreased in 50% of BAT‐PVN neurons, while a subset of BAT‐PVN neurons (20%) responded with an increase of sIPSC frequency following leptin application. Leptin did not change the resting membrane potential or input resistance of the recorded BAT‐PVN neurons. These data suggest that leptin contributes to the regulation of sympathetic outflow to the BAT via modulating the synaptic activity of PVN neurons.

Supported: NIDDK R01‐DK092587 (HM) and R01‐DK099598 (AZs).