bluuebunny/crossref_metadata_2025 huggingface dataset:
Alternate Quantification Approaches for Cold Induced Vasodilation in Human Glabrous Skin
Authors: Wilson Thad E , Gerow Daniel , Clegg Patrick , Metzler‐Wilson Kristen
Published: November 2023

Cold‐induced vasodilation (CIVD) is a phenomenon involving a counterintuitive increase in skin blood flow during cold exposure. Although CIVD was first described in 1930, CIVD mechanisms remain unknown. The majority of CIVD research has assessed vasodilation via skin‐surface temperature rather than direct assessment of skin blood flow. The study objective was to determine if laser‐Doppler flux, cutaneous vascular conductance (CVC), or skin erythrocyte concentration provides better assessment of CIVD. Twelve (8 men and 4 women) healthy (via health history and vital signs) subjects' laser‐Doppler flux, erythrocyte concentration, and skin‐surface temperature were measured in the left second and third fingers and right third finger, while arterial blood pressure (ABP) was measured in the right fourth finger on a beat‐by‐beat basis. The left hand was exposed to: baseline (10 min 22–23°C air), warming (10 min 35°C water), cooling (30 min 8°C water), and recovery (15 min 22–23°C air) and the right hand to 22–23°C air throughout. In addition to occurrence and mean data, beat‐by‐beat oscillations in skin blood flow were also analyzed via a fast‐Fourier transform binned within 0.009–0.02 Hz, 0.02–0.06 Hz, and 0.06–0.2 Hz. Temperature CIVD was observed in all participants, with an average of 2.33±0.98 occurrences. Flux and concentration CIVDs were observed in 11 and 9 subjects, respectively, with an average occurrence rate of 1.67±1.37 and 0.92±1.16, respectively. CVC increased during warming by 38.1±11.8% (P=0.006), then decreased during the first 5 min of cooling by 54.1±8.4% (P<0.001) but was not different by the end of cooling (P=0.143). Left hand second and third finger values and responses were congruent. In addition, left hand skin blood flow spectral power decreased during cooling compared to both baseline and warming within all bins (P<0.05), but no changes were noted during cooling (P>0.05). Right hand CVC was not initially altered but decreased by the end of opposite hand cooling (P=0.008). Right hand skin blood flow spectral power did not change across conditions (P>0.05). Cooling increased ABP by an average of 17.3±0.08% (P<0.001). These data indicate skin blood flow sympatholysis in the immersed hand during CIVD that is not observed in the non‐immersed hand. Direct measures of skin blood flow and erythrocyte concentration appear to add different aspects to the traditional indirect assessment of CIVD via skin surface temperature and may allow new investigations into CIVD mechanisms.
The Effect of Exogenous Adenosine Triphosphate on Blood Flow Kinetics During Dynamic Forearm Exercise
Authors: Shepherd John R. A. , Joyner Michael J. , Dillon Gabrielle A. , Dinenno Frank A. , Curry Timothy B. , Ranadive Sushant M.
Published: November 2023

Introduction

Adenosine triphosphate (ATP) is a vasodilating metabolite that plays a role in exercise hyperemia. In humans, exogenous infusion of ATP elevates skeletal muscle blood flow values to that observed during moderate‐intensity exercise. Recently ATP has been shown to evoke prolonged vasodilation over 150 minutes without tachyphylaxis. However, the steady‐state hyperemic responses to superimposed forearm exercise remain unaltered. The kinetics of blood flow during the initiation of exercise remains not well understood. Therefore we evaluated the effects of prolonged exogenous infusion of ATP on exercise hyperemia during the transition between rest and initiation of exercise.

Methods

While supine, eight healthy young participants (4M/4F; 25±1 years) performed 5 minutes of rhythmic dynamic handgrip exercise bouts (20% of maximum), first during saline (control), then at minute 5 and minute 150 during a continuous ATP infusion into the brachial artery. Each duty cycle consisted of 1 second contraction and 2 second relaxation. Mean blood velocity (MBV; cm/s), forearm vascular conductance (FVC; ml/minutes/100 mmHg), and shear rate (8*MBV/diameter; seconds−1) were calculated. The kinetics at the onset of exercise was assessed by calculating the slope of the FVC responses for the first 20 duty cycles after the start of contractions. Data are presented as means ± SEM.

Results

During saline control FVC was 3.9±0.3 at rest and with exercise rose to 22.7±0.84 and 27.8±1.2 ml/minute/100mmHg at 30 seconds and 1 minute, respectively (P<0.05 for both). Infusion of ATP increased FVC (3.9±0.3 vs 43.1±2.0 ml/minutes/100 mmHg, P<0.05) at five minutes and to 61.0±1.1 ml/minutes/100 mmHg at 150 minutes (P<0.05) with no systemic hemodynamic changes. Prolonged infusion of ATP did not alter the kinetics at the onset of contractions over 20 duty cycles of exercise hyperemic responses compared to control (0.71±0.1 control vs 1.01±0.1 ml/minutes/100mmHg/cycle at 5 minutes and vs 0.65±0.1 at 150 minutes, P>0.05 for all). Shear rate significantly increased compared to control (92±5 vs 751±57 seconds−1, P<0.05) but was not different across exercise responses during ATP infusion (751±57 at 5 minutes vs 549±46 seconds−1 at 150 minutes, P>0.05).

Conclusions

Our findings demonstrate that despite the ability of ATP to elevate blood flow to that observed during exercise, the blood flow kinetics for the initiation of dynamic exercise hyperemic response are unaffected and remain unaltered after 150 minutes of prolonged ATP infusion. Further investigation in needed to understand the role of ATP in regulating the blood flow kinetics during dynamic exercise in humans.

Support or Funding Information

This research was supported by National Institutes of Health Research Grants HL‐119337 and by CTSA UL1 TR000135. The Caywood Professorship via the Mayo Foundation also supported this study.
Effect of Normobaric Hypoxia Simulating 3,500 m on SpO2 and Workload in Women During Exercise at 65% VO2peak
Authors: Kambis Ken , Yasukawa Michio , Degarmo Anna , Quiroga Leonardo , Barbour Veronique , Muza Stephen , Looft‐Wilson Robin
Published: November 2023

While prior work (Muza, J. Appl. Physiol. 91: 2001) suggests that women and men have similar responses to high altitude, no studies have compared women's sea level VO2peak workload (W) to subsequent exercise performance in a normobaric hypoxic environment simulating an altitude of 3,500 m. As part of a larger study examining individual variability upon acute exposure to normobaric hypoxia, SpO2, heart rate (HR), and VO2peak (cycle ergometer) were measured in 24 female subjects at sea level (SL). No sooner than two days later, subjects entered a normobaric hypoxia chamber at 13.55% FiO2 approximating O2 partial pressures equivalent to those found at 3,500 m (HYPO).

METHODS

24 informed volunteer female subjects (20.8±0.9 yr.; 165.7±6.4 cm; 61.2±7.7 kg;

22.2±1.8 kg/m2; VO2peak 42.9±6.7 ml/kg/min; 185.7±9.5 bpm; 199±35W PeakPower) participated in this IRB approved study. All subjects were tested at SL then again 2+ days later after entering a normobaric hypoxia (FiO2=13.55%) chamber where SpO2 and HR were measured at rest and during exercise at a HR equivalent to that found at 65% SL VO2 peak.

RESULTS

Bonferroni t‐tests revealed no difference in SpO2 between the rest and exercise conditions at SL (98±1% vs 98±1%). As expected, there was a difference (P<0.01) between the SpO2 SL and HYPO conditions at both rest and exercise (Rest: 98±1% vs 88±3%; Exercise: 98±1% vs 85±4%). As expected, a difference (p<0.01; Bonferroni) between SpO2 in the HYPO rest and exercise conditions was noted (88±3% vs 85±4%). The difference between workload (W) at SL 65% VO2peak and 65% SL VO2peak (via matching HR) in the HYPO conditions (120±28W vs 76±19W) reflected a 36.2±11.9% decrease in relative work capacity (p<0.01; paired t‐test).

CONCLUSIONS

While the HYPO workload at 65% SL VO2peak was calculated from SL HR at 65% VO2peak, the results do indicate a large (36.2±11.9%) decrease in workload at a similar HR when acutely exposed to a normobaric hypoxic environment simulating an altitude of 3,500 m along with the typical exercise induced desaturation seen at altitude. These data suggest that there is a decrease in work capacity in women similar to that found in men by Van Cutsem et al. (Eur. J. Appl. Physiol., 115: 2015) who studied 9 men at 3800 m and found a 38% reduction in work capacity at 75% Wmax.

Support or Funding Information

The Doug Morton/Marilyn Brown Endowment for Biomedical Research, The Foundation for Aging Studies and Exercise Science Research, and The Borgenicht Program
Hypoxic Preconditioning Improves Respiratory Muscle Function during Hypoxia by Regulating Mitochondria in COPD Mice
Authors: Zuo Li , Chuang Chia‐Chen , Zhou Tingyang
Published: November 2023

Diaphragm weakness has been observed in patients with chronic obstructive pulmonary disease (COPD), which may be associated with the prolonged hypoxic conditions in the disease. We found that hypoxic preconditioning (HPC) can strengthen diaphragm under hypoxic conditions in COPD mice by treating the muscle with alternating low and high O2 concentrations. In this study, we tested the hypothesis that the protective effects offered by HPC are linked with the opening of mitochondrial ATP‐sensitive potassium channel (KATP) and the closing of the mitochondrial permeability transition pore (mPTP) in COPD mice. Adult C57BL6 mice were smoked for three months to develop COPD symptoms. Following the completion of smoking, diaphragms of the mice were isolated and mounted in a contractile chamber. Each muscle strip was treated (n = 6) or non‐treated with HPC (n = 6), or pre‐incubated with a combination of KATP channel inhibitor (glibenclamide; 100 μM) and mPTP opener (carboxyatractyloside; 50 μM; n = 6) for 30 min prior to HPC. Another two groups of muscles were treated either with KATP channel activator (diazoxide; 100 μM; n = 6) or mPTP inhibitor (cyclosporine A; 100 μM; n = 6) in the absence of HPC. The muscles were then consecutively stimulated for five minutes (0.5 Hz) during a 30‐min hypoxic period. Fatigue tolerance was determined as the ratio of residual force at the end of the five‐min contraction to the initial force. Data were expressed as means ± SE, and analyzed using multi‐way ANOVA. P < 0.05 was considered statistically different. Our results show that HPC significantly improved diaphragm function during hypoxia (29 ± 2.8% for HPC vs. 6 ± 1.3% for control, p < 0.05). However, such protective effects were eliminated via the simultaneous inhibition of KATP channel and the opening of mPTP (5 ± 2.1%, p < 0.05 vs. HPC). On the other hand, either the activation of KATP channel (27 ± 2.6%) or the inhibition of mPTP (24 ± 3.6%) significantly mitigates diaphragm fatigue (p < 0.05 vs. control) to an extent similar to that of HPC. These data collectively indicate that the mechanisms of HPC protection on diaphragm under hypoxia may involve the opening of mitochondrial KATP channel and inhibition of mPTP in COPD mice.

Support or Funding Information

American Physiological Society (APS) 2016 S&R Foundation Ryuji Ueno Award
Ventilatory and Carotid Body Chemosensory Responses In Rats Exposed To Short‐Term Sustained Hypoxia
Authors: Flor Karine C. , Silva Elaine F. , Menezes Miguel F. , Pedrino Gustavo R. , Colombari Eduardo , Zoccal Daniel B.
Published: November 2023

Previous studies performed in in situ rat preparations reported that the exposure to short‐term (24 h) sustained hypoxia (SH) generates active expiration at rest, increases baseline sympathetic activity during expiration and enhances sympathetic responses to peripheral chemoreceptor stimulation. In the present study, we evaluated basal and hypoxic‐induced changes in ventilatory parameters of unanesthetized juvenile male Holtzman rats (80–90 g) previously exposed to SH (10% O2, 24 hs). In addition, we examined the chemosensory response of carotid body chemoreceptors of decerebrated, artificially‐perfused in situ preparations of juvenile rats (60–80 g) submitted to SH. At resting conditions, SH rats (n=12) exhibited augmented (P<0.05) respiratory frequency (109±2 vs 97±1 cpm), tidal volume (14±1 vs 10±1 ml/kg) and minute ventilation (1550±137 vs 979±114 ml/kg.min) compared to control rats (n=12). SH rats also showed greater tachypneic and hyperventilatory responses (P<0.05) to a new hypoxia episode (7% O2, 20 min) in comparison to control rats. The magnitude of increase in tidal volume was similar between groups. The in situ preparations of SH rats (n=8), but not controls (n=8), exhibited additional bursts in baseline abdominal motor activity, indicating the presence of active expiration at rest. Interestingly, basal afferent activity of carotid sinus nerve (CSN) was similar (0.67±0.18 vs 0.65±0.18 μV) between SH and control rats. Moreover, the CSN excitatory response to stimulation of peripheral chemoreceptors with potassium cyanide was not different between groups (ΔCSN: 1235±372 vs 922±278 %), although the in situ preparations of SH rats showed greater sympathoexcitatory reflex responses (P<0.05). Our findings indicate that augmented basal ventilation and enhanced ventilatory and sympathetic responses to hypoxia in rats exposed to SH are not dependent on increased basal and sensorial activity of carotid body chemoreceptors, but may rely on central mechanisms.

Support or Funding Information

FAPESP (2013/17.251‐6) and CNPq
Zinc deficiency worsens and zinc supplement prevents the development of diabetic cardiomyopathy, respectively, in the db/db mice: A key role of Nrf2
Authors: Wang Bowei , Wang Shudong , Tong Jian , Wang Yuehui , Cai Lu
Published: November 2023

Diabetic cardiomyopathy (DCM) is highly prevalent in the type 2 diabetic (T2DM) patients. Zinc is one of the important essential trace metals, and its deficiency associates with various chronic pathogenesis, including vascular diseases. We used B6.BKS(D)‐Leprdb/J (db/db) mice as a T2DM mouse models and provided mice, for six months, with normal diet containing three levels of zinc: deficient, adequate, and supplemented, to explore the role of zinc in the development or progression of DCM. Cardiac function, reflected by the EF%, was significantly decreased along with increases in left ventricle mass and the ratio of heart weight to tibial length, in the db/db mice. As molecular cardiac hypertrophy marker, ANP protein was also significantly increased in db/db mice. The cardiac dysfunction and hypertrophy were also accompanied with significant increases in fibrotic responses (accumulated collagens and increased TGF‐β and CTGF expression) and inflammatory responses and signalings (increased expression of TNF‐α, IL‐1β, CARD9, and BCL10 and activated p38 MAPK) in the heart of db/db mice. All these diabetic effects were exacerbated and ameliorated by zinc deficiency and zinc supplement, respectively. Mechanistically the oxidative stress and damage, mirrored by 3‐NT and 4‐HNE, was significantly increased along with significant decrease in the expression of Nrf2 and its down‐stream antioxidants (NQO‐1 and catalase), which was exacerbated and ameliorated by zinc deficiency and zinc supplement, respectively, in the heart of the db/db mice. These results suggest that zinc deficiency worsens the pathological progression of cardiac disorders in type 2 diabetic db/db mice, which can be significantly prevented by zinc supplement, all which may be related to the role of Nrf2 in the prevention of DCM development and progression.

Support or Funding Information

This work was supported in part by the Scholarship of China Scholarship Council(No.201506175180)
Telomerase deficiency predisposes to heart failure and ischemia‐reperfusion Injury
Authors: Ait‐Aissa Karima , Heisner James S , Strande Jennifer L , Harmann Leanne , Camara Amadou K.S. , Beyer Andreas M
Published: November 2023

Introduction

Coronary heart disease remains one of the main cause of death worldwide. With lack of successful treatment, new therapeutic targets and effective treatments are yet to be discovered.

Hypothesis

Our preliminary results suggest a strong correlation between telomerase impairment and impaired mitochondrial respiration in hearts from human subjects with coronary artery disease. Additionally, it has been shown that acute overexpression of the catalytic subunit of telomerase, TERT, increases survival rate and decreases infarct size in left anterior descending artery ligation mice model. In the present study, we examined the role of TERT on cardiac structure and function under baseline conditions and following ischemic stress.

Methods

Transthoracic echocardiogram was performed on wild‐type (WT) and TERT knockout rats (TERT−/−) to assess cardiac structure and function. To evaluate heart function further, Langendorf model was used to evaluate the effects of acute global ischemia reperfusion (I/R) on cardiac function and infarction.

Coronary Flow (CF) and left ventricular pressure (LVP) were measured continuously online before, during and after 30 min no flow global ischemia. Functional data were assessed at 60 min reperfusion while infarct sizes were determined at the end of the 120 min reperfusion using TTC staining.

Results

Echocardiographic analysis revealed early singes of diastolic heart failure in TERT−/− rats. No change in CF or LVP was found during pre‐ischemia, however, at 60 min reperfusion); infarct size was reduced in TERT−/− rats (TERT−/−: 36±2%*; WT: 42±1%; n=7–8; *p<0.05). Functionally TERT−/− had decreased recovery as Isovolumic relaxation time was decreased (TERT−/−: 11.36±0.74ms*; WT: 13.9±0.59ms; n=12; *p<0.05) while E velocity was elevated more in TERT−/− (TERT−/−:1.15±0.03ms*; WT: 1.02±0.04ms; n=12; *p<0.05) suggesting a component of diastolic dysfunction in the setting of increased intracardiac pressures.

Conclusion

TERT deficiency causes additional cardiac dysfunction unrelated to the degree of myocardial necrosis suggesting underlying metabolic defects in TERT−/− rats. These results suggest a therapeutic role of telomerase to prevent heart failure after myocardial infarction.
Spinal Dorsal Column and Vagus Nerve Stimulation Modulate Vagal Afferent Transduction of Myocardial Ischemia
Authors: Salavatian Siamak , Beaumont Eric , Armour John Andrew , Ardell Jeffrey L.
Published: November 2023

Background

Autonomic regulation therapy (ART), including vagus nerve stimulation (VNS) and spinal cord stimulation (SCS), is an emerging therapy in managing heart diseases, doing so by modulating multiple elements of the cardiac neuronal hierarchy.

Objective

To determine if ART impacts primary cardiac sensory afferent transduction of myocardial ischemia (MI).

Methods

Using extracellular recordings in 19 anesthetized canines, 36 cardiac‐related nodose ganglia neurons were identified by their response to epicardial touch, great vessel occlusion (inferior vena cava occlusion and descending aorta), left anterior descending (LAD) coronary artery occlusion(CAO) and chemical activation of sensory neurites with epicardial veratridine. Neural responses to 1 min LAD CAO were then evaluated prior to and following either SCS [T1–T3 spinal level; 50Hz, 90% motor threshold] or cervical VNS [15–20 Hz; 1.2× threshold]. Cardiac nodose neural activity was also assessed at progressive levels of VNS [2 Hz; 1–8 mA].

Results

66% of cardiac‐related nodose neurons responded to LAD CAO, with activity increasing ~140% (0.33±0.08 to 0.79±0.19 Hz, p=0.001). The neural response to LAD CAO was suppressed by SCS (0.85±0.3 to 0.11±0.4 Hz, p=0.03) or VNS (0.74±0.26 to 0.11±0.05 Hz, p=0.03). Nodose neural activity increased progressively with VNS current from 1 to 5 mA (0.2±0.1 to 0.69±0.1 Hz, p=0.005) but decreased when VNS current exceeded 5 mA (0.69±0.1 to 0.12±0.08 Hz, p=0.004).

Conclusions

LAD CAO activates multi‐modal and nociceptive afferent inputs to the central nervous system. VNS and SCS have the capability to obtund this afferent response, likely doing so by modifying the myocyte/nerve interface. Cardiac nodose neurons did not show linear response to progressive VNS, indicating they are not simple relay stations, and these processing capabilities of the nodose include a damping function in response to excessive neural input.

Support or Funding Information

none.
Calcium Inhibition of Oxidative Phosphorylation
Authors: Bazil Jason N , Zhang Yizhu
Published: November 2023

Calcium induced mitochondrial dysfunction is an important event that occurs during ischemia/reperfusion injury. But the details and precise mechanism of inhibition are obscure. Here we show that ADP stimulated respiration (state 3) is inhibited by calcium in a titratable manner. Isolated cardiac mitochondria from guinea pigs were exposed to varying levels of calcium while respiration was monitored using an Oroboros O2k oxygraph. The levels of calcium used are below the mitochondrial permeability transition threshold and reveal an additional component of calcium induced mitochondrial dysfunction that occurs during ischemia. Calpain I, II, and III inhibitors, as well as, calpeptin had little to no effect suggesting a mechanism other than calcium‐activated proteases leading to the decrease in state 3 respiration. In addition, unloading of mitochondrial calcium did not ameliorate the calcium‐induced state 3 dysfunction. The presence of extra‐mitochondrial ATP did protect against calcium; however, this was primarily due to calcium chelation. Higher levels of calcium to compensate for ATP complexation depressed state 3 respiration; however, a protective effect of ATP was still observed. The physiological implications for this phenomenon is significant for the ischemia/reperfusion paradigm.

Support or Funding Information

This work was supported by NIH grant R00‐HL121160.
Exogenous Ubiquitin Improves Cardiac Function and Reduces Inflammatory Response Following Myocardial Ischemia/Reperfusion Injury
Authors: Scofield Stephanie L.C. , Lim Kristina A. , Dalal Suman , Singh Mahipal , Singh Krishna
Published: November 2023

Ischemia/reperfusion (I/R) model represents a clinically relevant animal model to parallel the inflammatory and remodeling response associated with myocardial infarction. Ubiquitin (UB) is a small molecular weight protein best known for its role in the proteasomal degradation of damaged proteins. Previously, our lab demonstrated that sympathetic stimulation increases extracellular levels of UB independent of necrosis, and extracellular UB ameliorates the adverse effects of chronic sympathetic stimulation, namely: increases in workload, function and myocyte apoptosis. Here we tested the hypothesis that extracellular UB decreases inflammatory response in the heart, thereby playing a protective role in myocardial ischemia/reperfusion injury. This study used 8–12 week male C57Bl/6 mice. One day prior to ischemia/reperfusion injury, mice were infused with vehicle (saline) or UB (1μg/g/h) using micro‐osmotic pumps which osmotically released UB over 3 days. The hearts were subject to ischemia for 45 min followed by reperfusion for 3 days. Heart function was assessed by m‐mode echocardiography and measured in terms of percent fractional shortening (%FS) and ejection fraction (%EF). Infarct size was determined using Masson's trichrome staining of heart sections. Inflammatory response was measured using hematoxylin and eosin (H&E) staining, and by immunohistochemical staining using anti‐neutrophil and anti‐F4/80 (macrophage) antibodies. Infarct size was significantly smaller in UB‐infused group (% of LV infarcted; Vehicle‐I/R, 26.7±4.4; UB‐I/R, 13.0±2.7*; *P<0.05 vs Vehicle‐I/R; n=5). Echocardiographic analyses showed that I/R decreases heart function as measured by decreased %FS and %EF versus sham. UB treatment significantly improved %FS (Sham, 37.9±2.8; UB, 34.9±1.3; Vehicle‐I/R, 28.3±1.1*; UB‐I/R, 33.0±1.8$; *p<0.05 vs Sham $p<0.05 vs Vehicle‐I/R; n=6–7) and %EF (Sham, 68.5±3.6; UB, 64.9±3.6; Vehicle‐I/R, 55.6±1.8*; UB‐I/R, 62.4±2.6$; *p<0.05 vs Sham $p<0.05 vs Vehicle‐I/R; n=6–7) when compared to Vehicle‐I/R group. H&E staining showed a significant decrease in inflammatory cells in UB‐I/R group (total infiltrates per 0.1mm2; Vehicle‐I/R, 106.6±15.9; UB‐I/R, 46.5±6.8*; *p<0.05 vs Vehicle‐I/R; n=3). Likewise, the number of neutrophils and macrophages was significantly lower in UB‐infused hearts following I/R injury. These data suggest that exogenous UB decreases infarct size, improves heart function and decreases inflammatory response following I/R injury. Thus, exogenous UB plays a protective role in myocardial I/R injury, possibly by limiting the extent of inflammatory response.

Support or Funding Information

Supported by Department of Veterans Affairs (BX002332), NIH R15HL129140 (NHLBI) and Institutional Research and Improvement account.
SIRT1 Activator II Protects against Myocardial Injury in High Fat Diet‐Induced Diabetic Mice
Authors: Boini Krishna M , Raghunathan Suchi , McConnell Bradley , Koka Saisudha
Published: November 2023

Cardiovascular diseases are a leading cause of death and disability in diabetic patients. Recent studies suggest that switching gears towards survival and longevity factors such as sirtuins induce protection against cardiovascular complications in diabetic patients. The present study investigated the effect of SIRT1 activator II on myocardial injury in high fat diet‐induced type 2 diabetic mice. Adult C57BL/6J mice (n=16/group) were fed a normal chow diet (ND‐10 Kcal % fat) or high‐fat diet (HFD‐60 Kcal % fat) for 6 months. Body weights and blood glucose levels were monitored. Glucose tolerance tests were performed after dietary intervention to confirm the development of type 2 diabetes. A subset of HFD mice were treated with SIRT1 Activator II for 4 weeks. Plasma was collected from mice to measure plasma glucose, insulin and lipid parameters such as total cholesterol, HDL and LDL/vLDL. Subsequently mice hearts were isolated and subjected to 20 min ischemia and 40 min reperfusion (I/R). SIRT1 Activator II treatment significantly reduced the body weight (42.5±1.1 g vs 50.9±1.5 g; p<0.05), fasting plasma glucose levels (210.1±24.6 mg/dl vs 354.7±19.7 mg/dl; p<0.05) and insulin (3.97±1.45 ng/ml vs 12.11±2.01 ng/ml; p<0.02) compared to untreated HFD group. SIRT1 activator II treatment improved the lipid profile in HFD mice. Functional recovery after I/R in the ex vivo Langendorff perfusion model was significantly lower in HFD fed mice than ND fed mice. SIRT1 activator II treated mouse hearts demonstrated better cardiac function recovery and had significant reduction of the necrotic markers creatine kinase and lactate dehydrogenase. SIRT1 activator II significantly reduced the infarct size (22.08±2.2% vs 35.418±3.79% p<0.01) in HFD fed mice following I/R injury. Additionally, SIRT1 Activator II treatment suppressed expression of proinflammatory cytokines in HFD fed mice. In conclusion, our findings suggest that SIRT1 activator II prevents the detrimental effects of diet‐induced type 2 diabetes and could be a safe therapeutic intervention for ischemic heart diseases in diabetic patients.

Support or Funding Information

DK104031
The Role of Cardiac Lineage Protein 1 (CLP1) on Inflammatory and Fibrotic Responses following Myocardial Infarction
Authors: Ghobrial Christine , Salciccioli Louis , Stewart Mark
Published: November 2023

Cardiovascular disease is one of the leading causes of death worldwide. Atherosclerosis, for example, can contribute to loss of blood supply to the heart, and damage or destroy cardiomyocytes. Sufficient damage leads to heart failure. Cardiomyocyte loss results in a process of remodeling, which includes inflammatory responses that remove debris, followed by fibroblast transdifferentiation to replace muscle tissue. Cardiac lineage protein 1 (CLP1) is a regulatory protein that is involved in directing cardiac development (Huang, et al. Gene. 2002;121(6):559–72). We studied whether CLP1 plays a role in remodeling the heart following permanent left anterior descending artery (LAD) occlusion in mice. Specifically, we sought to determine the role of CLP1 in the development of fibrosis in cardiac tissue, and to changes in the expression activity of Smad3 and NFkB, key transcription factors which are involved in myocardial infarction.

All mice were imaged using echocardiography preoperatively and once a week, postoperatively. Wildtype and CLP1+/− mice either underwent sham surgery or LAD occlusion (Gao, et al. Circ Res. 2010;107(12):445–1453). The hearts were harvested at 1 week or at 4 weeks following surgery and were processed for histological analysis of fibrosis or for biochemical and immunohistochemical analysis of inflammatory pathways involved in myocardial infarction.

Wildtype and CLP1+/− hearts exhibit cardiac remodeling, as measured by percent of collagen deposition both above and below the ligation. CLP+/− hearts had a lower amount of remodeling both above and below the ligation following ischemic injury compared to wildtype 1 week following permanent LAD occlusion. However, at 4 weeks following ischemic damage, there was a significantly greater amount of remodeling in the CLP1+/− mice compared to wildtype mice both above and below the ligature. Immunofluorescence staining showed increased pSmad3 and pNFkB activation and translocation into the nucleus in the infarcted zone following ischemic damage in both wildtype and in CLP1+/− hearts. Cardiac function in CLP1+/− mice was worse in comparison to the wildtype, as measured by fractional shortening and by ejection fraction both 1 week and 4 weeks following MI. There was not a statistically significant difference in LVmass between CLP1+/− and wildtype mice.

Our data suggest that CLP1 limits the remodeling response by possibly delaying the fibrotic phase of myocardial infarction injury. This may result from a prolonged inflammatory period, and a delay in collagen deposition in the infarcted area, thus resulting in a poorer functional recovery after ischemic damage. Limiting the duration of inflammation may result in a better prognosis following myocardial infarction.
Lower Limb Venous Distension Reflex and Orthostatic Tolerance in Young Healthy Humans
Authors: Cui Jian , Blaha Cheryl , Herr Michael D. , Sinoway Lawrence I.
Published: November 2023

We and others showed that venous distension induced by saline infusion into veins of an arterially occluded arm evokes reflex increases in muscle sympathetic nerve activity (MSNA) and blood pressure (BP) in humans (i.e. venous distension reflex). Our recent report also shows that suction of arterially occluded limb (forearm or lower leg) evokes significant increases in MSNA and BP, which are induced by the vascular distension in the limbs. We postulate that venous distension reflex will be activated when humans stand. We speculate that the individual differences in the venous distension reflex may contribute to the individual differences in the orthostatic tolerance. Thus, we hypothesized that the orthostatic tolerance would be related with the MSNA response to the lower limb suction. Fifteen healthy subjects (8M, 7F, 26 ± 1 yrs, 172 ± 3 cm, 69 ± 4 kg) were tested in supine position. One of the subject's lower legs was inserted into an airtight pressure tank. An arterial occlusion cuff was put on the mid thigh (~10–15 cm above the level of the suction tank). MSNA (in the opposite limb), ECG, and BP (Finometer) were recorded throughout the study. After the arterial occlusion cuff on the mid thigh was inflated (250 mmHg), limb suction (‐100 mmHg) is applied for 2 min. Limb occlusion without suction was used as a control trial. In a separate visit, the individual's orthostatic tolerance was assessed using a graded lower body negative pressure (LBNP) tolerance test (from 20 up to 70 mmHg, no MSNA). Mean arterial BP (MAP, 78.9 ± 1.1 to 86.9 ± 1.7 mmHg) and MSNA (18.5 ± 1.9 to 23.6 ± 2.0 bursts/min) significantly (both P < 0.05) increased during the suction of a leg, while heart rate was not significantly different from the baseline. Occlusion alone did not significantly alter MSNA. The magnitude of the MSNA response to single leg suction at 100 mmHg was then compared to the orthostatic tolerance index for that subject. The orthostatic tolerance index positively correlated (R = 0.636, P = 0.011) with the MSNA response seen with suction during occlusion. The presented data suggest that the venous distension reflex strength correlates with the level of orthostatic tolerance. Thus, we speculate that lower limb venous distension reflex engagement increases the sympathetic responses during orthostatic challenge and serves to maintain BP with postural stress.

Support or Funding Information

Supported by American Heart Association Grant 15GRNT24480051 (Cui), National Institutes of Health Grants P01 HL096570 (Sinoway) and UL1 TR000127 (Sinoway).
Presynaptic organization of CaV2 channels with specific vesicle pools in SCG vs rat tail artery
Authors: Kalkhoran Somayeh Mojard , Walia Jag , Gershome Cynthia , Chow Sarah HJ , Poburko Damon
Published: November 2023

Peripheral sympathetic nerves co‐release multiple neurotransmitters to modulate the activity of their target organ, for example mediating physiological regulation of cardiac contractility and systemic vascular tone. However, the release of “co‐released” transmitters like norepinephrine (NE) and ATP can be differentially regulated, for example by relying on specific isoforms of voltage‐gated Ca2+ channels (CaV), and we previously reported that NE‐ and ATP‐containing vesicles segregate in pools that preferentially co‐localize with specific CaV2 isoforms in rat tail artery. Whether this observation generalizes to other sympathetic nerves is not known, but it is of fundamental importance to understanding the molecular biology of sympathetic co‐release.

OBJECTIVE

To determine whether specific isoforms of CaV selectively associate with pools of vesicles enriched with transporters for NE or ATP in multiple peripheral sympathetic nerves.

METHODS

We performed epifluorescence imaging of intact rat tail artery and cultured superior cervical ganglia (SCG) neurons, comparing the localization and intensity correlation of CaV2.1, CaV2.2, and CaV2.3 with vesicle markers for NE (VMAT2) and ATP (VNUT/SlC17A) containing vesicles or suitable surrogate markers.

RESULTS

We confirmed that VMAT2 and VNUT are often but not always found in the same varicosities. While VMAT2 is broadly distributed in varicosity, VNUT localizes as discrete puncta at the perimeter of varicosity and does not co‐localize with synaptagmin1 in SCG neurons, similar rat artery nerves. CaV2.3 and CaV2.1, like VNUT, localize to the periphery of the varicosities, while CaV2.2 more closely mimics to the distribution of VMAT2. These findings mirror our observations in rat tail artery, in which NE release is most sensitive to CaV2.2 inhibition and ATP‐mediated contraction is blocked by CaV2.3 inhibition.

CONCLUSION

We show that synaptic organization of CaV2 isoforms with specific pools of vesicle in a cultured nerve system closely recapitulates that found in vivo. This observation further validates cultured SCG neurons as an experimentally tractable and physiologically revenant model to study presynaptic cell biology relevant to the regulation of both cardiac output and vasoregulation.

Support or Funding Information

1. Natural Sciences and Engineering Research Council of Canada.2. Canadian Foundation for Innovation
Acute and Chronic Increases in Sodium and Cardiac Vagal Baroreflex Sensitivity
Authors: Babcock Matthew C , Watso Joseph , Brian Michael S , Edwards David G , Stocker Sean D , Wenner Megan M , Farquhar William B
Published: November 2023

Elevations in serum sodium (sNa+) and plasma osmolality (pOsm) have been shown to increase baroreflex sensitivity. However, the time course of these changes is not clear.

PURPOSE

To determine whether acute and/or chronic elevations in sNa+ and pOsm alter cardiac baroreflex sensitivity (cBRS) and heart rate variability (HRV).

METHODS

An acute increase in sNa+ was achieved with a 23‐minute hypertonic saline infusion (HSI) in 14 subjects (age: 22±1 yrs, BMI: 23±1 kg/m2, 7 men). A chronic increase in sNa+ was achieved with 7 days of a high sodium diet (300 mmol/day) compared to 7 days of a low sodium diet (20 mmol/day; diet order randomized) in 16 subjects (age: 39±4 yrs, BMI: 23±1 kg/m2, 7 men). In the acute and chronic protocols, subjects lay quietly for 5 minutes while undergoing simultaneous measurement of beat‐to‐beat blood pressure (via photoplethysmography) and R‐R interval (via 3‐lead ECG). cBRS was evaluated using the sequence method. Root‐mean‐square of successive differences in R‐R interval (RMSSD) was used as an index of HRV.

RESULTS

HSI increased sNa+ (137.9±0.4 vs. 140.9±0.5 mEq/L, p<0.05) and pOsm (285±1 vs. 290±1 mOsm/kg H2O, p<0.05). Despite these acute increases, cBRS (26±5 vs. 27±4 ms/mmHg, p=0.73) and RMSSD (63±9 vs. 63±8 ms, p=0.99) were not different. High sodium diet similarly increased sNa+ (137.3±0.6 vs. 140.0±0.4 mEq/L, p<0.05) and pOsm (285±1 vs. 290±1 mOsm/kg H2O, p<0.05). cBRS was significantly increased on the high sodium diet (18±2 vs. 25±3 ms/mmHg, p<0.05), as was RMSSD (61±6 vs. 84±10 ms, p<0.05).

CONCLUSION

These preliminary data suggest that chronic, but not acute, elevations in sNa+ and pOsm are associated with increases in cBRS and HRV.

Support or Funding Information

Supported by NIH Grant 1R01HL128388‐01A1
Non‐Invasive 3‐Dimensional Facial Modeling for the Quantification of Facial Edema
Authors: Smith Bridget , Crowell Brent , Ozgur Omar , Goetchuis Elizabeth , Newby Nate , Scott Jessica
Published: November 2023

BACKGROUND

With the lengthening of spaceflight mission durations, many crewmembers have experienced in‐flight and/or post‐flight visual and anatomical changes including optic‐disc edema, globe flattening, choroidal folds, and hyperopic shifts. These changes define the visual impairment/intracranial pressure (VIIP) syndrome. Although the underlying mechanism behind VIIP is unknown at this time, it is suspected that the microgravity‐induced cephalad fluid shift plays a significant role. Therefore, quantification of the microgravity‐induced fluid shifts may provide important prognostic information. However, there are limited non‐invasive tools currently available to assess volume changes and facial edema. A standardized method for quantifying the fluid shift and establishing reliability across repeated trials also remains to be clarified. Accordingly, using a commercially available Structure Sensor 3‐dimensional (3D) scanner, our lab developed a protocol to acquire and analyze 3D facial images in seated and supine positions and assessed the validity and reliability of the method. We hypothesized that within day coefficient of variation and across day coefficient of variation would be low (<5%).

METHODS

Volume measurement validity was assessed by acquiring and analyzing 3D scans of an object with a known volume across three trials. Reliability was assessed in 10 subjects. Structure Sensor 3D scanner (Occipital Inc., San Francisco, CA) images were obtained in two positions: upright and supine on three separate days. Images were immediately viewed on an Apple IPad with ItSeezit3D (ItSeez3D Inc., San Francisco, CA) application to ensure complete scans were obtained. Participants were instructed to look at the same spot each time to ensure constancy across scans. Analysis was completed in Rhinoceros (Robert McNeel & Associates, Seattle, WA, version 5, 64‐bit) software with a standardized technique developed by our lab.

RESULTS

Validity assessments yielded a mean absolute difference of 1.13 in3 . Average intra‐trial and intra‐day variability (CV) was 2.79%. Upon initial analysis, a cephalic fluid shift was evident in participants in a seated position when compared to the supine position. The mean fluid shift across participants was approximately 600 mL.

CONCLUSION

Our findings indicate that the Structure Sensor 3D scanner and accompanying analysis software are valid and reliable tools in the assessment of cephalic fluid shift across different positions. This technology may be useful in identifying inter‐individual differences in cephalic fluid shifts in crewmembers. Future studies should examine the potential applications of this technology in response to a microgravity environment.
Lgr5 Stem Cell‐based organoids in human disease
Authors: Clevers Hans
Published: November 2023

The intestinal epithelium is the most rapidly self‐renewing tissue in adult mammals. We originally defined Lgr5 as a Wnt target gene, transcribed in colon cancer cells. Two knock‐in alleles revealed exclusive expression of Lgr5 in cycling, columnar cells at the crypt base. Using lineage tracing experiments in adult mice, we found that these Lgr5+ve crypt base columnar cells (CBC) generated all epithelial lineages throughout life, implying that they represent the stem cell of the small intestine and colon. Lgr5 was subsequently found to represent an exquisitely specific and almost ‘generic’ marker for stem cells, including in hair follicles, kidney, liver, mammary gland, inner ear tongue and stomach epithelium.

Single sorted Lgr5+ve stem cells can initiate ever‐expanding crypt‐villus organoids, or so called ‘mini‐guts’ in 3D culture. The technology is based on the observation that Lgr5 is the receptor for a potent stem cell growth factor, R‐spondin. Similar 3D cultures systems have been developed for the Lgr5+ve stem cells of human stomach, liver, pancreas, prostate and kidney. Using CRISPR/Cas9 technology, genes can be efficiently modified in organoids of various origins.
Differential Effect of Testosterone Supplements on Body Composition in Young and Old Male Spontaneously Hypertensive Rats
Authors: Maranon Rodrigo Oscar , Dalmasso Carolina , Patil Chetal N , Cardozo Licy L Yanes , Juncos Luis A , Reckelhoff Jane F
Published: November 2023

The use of testosterone supplements (T) is increasing in the US and is mainly used for conditions such as treatment of hypogonadism, to increase libido, strength, and physical resistance, and to prevent osteoporosis. While clinical and experimental evidence shows that T could improve metabolic parameters in obese men with hypogonadism, T could impair the cardiovascular system leading, for example, to elevated blood pressure. However, these data are controversial. Previously in our lab, we found that T increased blood pressure (BP) in young male spontaneously hypertensive rats (SHR), whereas in old male SHR, T had the opposite effect causing a decrease in BP. We had previously found that T improved metabolic syndrome and caused weight loss with an increase in activity in male obese Zucker rats. Whether T has an effect on body composition in young or old male SHR is unknown. In the present study, we tested the hypothesis that T in young (YSHR) and old (OSHR) male SHR changes body composition mainly by decreasing food intake and body weight. YSHR and OSHR were given testosterone propionate (22 mg/10 mm silastic pellet, sc) or placebo (empty pellets, sc), beginning at 16 weeks and 18 months of age for 6 weeks, respectively. T increased the plasma testosterone (RIA) by +2.5 fold in YSHR and +4 fold in OSHR (p<0.05). T increased plasma estradiol (RIA) by +2 fold in YSHR and 1 fold in OSHR (p<0.05). Tibia lengths were not affected by T in YSHR or OSHR. T reduced food intake in YSHR by 21% compared to YSHR+P (p<0.05), body weight by 8% (p<0.05), total water content by 19% (106±4 vs 87±6, p<0.05), and fat mass by 49% (4.9±0.6 vs 2.5±0.4 % BW, p<0.05), but had no effect on lean mass (p=NS) (all measured by ECHO MRI). Contrary to our hypothesis, while T modestly reduced FI by 12% in OSHR (26±1 vs 23±1 gr, p<0.05), there was no effect on BW, fat mass, total water content, or lean mass after 6 weeks of T supplementation. These data suggest that T supplements in young individuals can modulate body weight and FI and may contribute to an improvement in metabolic parameters. While not addressed in this study, the data also suggest that T supplementation needs to be reevaluated considering the risk for cardiovascular events in aging men who are overweight or obese.

Support or Funding Information

Supported by NIH‐R01HL66072, PO1HL51971 (JFR), 14POST18640015 (ROM), EFF Endocrine Res Grant (LLY).
Sexual Dimorphic Responses of Renal Transporters to High Salt Diet Favor More Diuresis in Females
Authors: Veiras Luciana Cecilia , Lisboa Hector , Khalil Zoya , Ralph Donna Lee , McDonough Alicia Ann
Published: November 2023

We previously reported, in male rats, that high salt diet (HSD) increased proximal tubule (PT) Na+/H+ exchanger phosphorylation (NHE3pS552), a marker of its inactivation, depressed total abundance of distal tubule Na+‐Cl− cotransporter (NCC), and redistributed apical Na+ transporters to higher density fractions (Yang LE, AJP Renal, 2008). Female rats and mice have lower abundance of proximal tubule sodium transporters (NHE3, NaPi2) and higher abundance and phosphorylation (activation) of NCC as well as cleaved (activated) epithelial sodium channels' (ENaC) α and g subunits (FASEB J, 2016, 30: Supp 967.29). Female mice also have a more robust pressure natriuretic response than males (Mirabito KM et al, AJP Renal, 2014). Based on this background, this study aimed to compare the responses of females (F) and males (M) to high salt diet; we postulated that F would exhibit more robust responses than M.

Methods

C57Bl/6 mice (n=5/group) received normal salt diet (0.26% NaCl; MNS: males normal salt; FNS: females normal salt) or a high salt diet (4.0% NaCl; MHS: males high salt; FHS: females high salt) for two weeks. Transporter and channel abundance were determined by quantitative immunoblot in homogenates of renal cortex. The Figure displays the fold change in the abundance of transporters and channels after HSD, relative to NSD in F and M.

Results

Females had a greater diuretic response to HSD (6 fold) than M (ns). At baseline, F had lower PT NHE3 (0.6‐fold) and lower NHE3pS552 (0.7‐fold) than M. NHE3pS552 increased 0.2‐fold in MHS, and was unchanged in FHS. Along the loop and distal nephron, there was no significant difference in Na+‐K+‐2Cl− cotransporter isoform 2 (NKCC2), NKCC2pT96T101, NCC, or NCCpS71 at baseline, yet SPAK, a regulatory kinase that phosphorylates these cotransporters and claudin 7 were elevated in F (0.5‐ and 0.7‐fold, respectively). In FHS NKCC2, NKCC2pT96T101, NCC, and NCCpS71 were lower than FNS (0.2‐, 0.5‐, 0.3‐, 0.5‐fold, respectively) and in MHS vs. MNS only NCC decreased (0.2‐fold) suggesting less Na+ reabsorption in this nephron region in F vs. M. In collecting duct at baseline, ENaC γ was higher in F than M (0.15‐fold) and doubled in both FHS and MHS vs. NS. ENaC γ subunit cleavage decreased 0.2‐fold only in MHS. Taken together, these results demonstrate that the responses to HS diet are sex dependent. The more robust diuresis in FHS can be attributed to lower PT NHE3 at baseline as well as reduced NKCC2, NKCC2pT96T101, NCC and NCCpS71 during HS diet. These characteristics likely facilitate pressure natriuresis and contribute to lower blood pressures in females.

Support or Funding Information

NIH R01DK 083785, AHA 15GRNT23160003