bluuebunny/crossref_metadata_2025 huggingface dataset:
Sex differences in a novel transgenic mouse model of Alzheimer’s Disease
Authors: Smith Cassandra N. , Shahab Nusaira Beenta , Weiss Robert M. , Zimmerman Kathy , Yang Liping , Sabharwal Rasna
Published: May 2024

Alzheimer’s disease (AD) is the most common form of dementia characterized by memory deficits, cognitive impairment, and presence of amyloid plaques and tau tangles in the brain. In the United States, six million people over the age of 65 live with AD, four million of whom are women. The apolipoprotein ( APOE) gene is the strongest genetic risk factor for late-onset AD, with the ε4 allele increasing AD risk relative to the ε3 allele. Mechanisms driving sex-based prevalence in the APOE4 genotype remain unknown. Previously, we have reported that female APOE4 mice develop hypertension and increased levels of vasoconstrictor angiotensin II (Ang II) in CSF with aging [FASEB J 2022: 36S1]. To better recapitulate human AD pathology and phenotype, we have recently generated unique mouse strains - 3XE4 and 3XE3 mice, by breeding human APOE4/APOE3-knockin with APPsw, PS1dE9, and tauP301S transgenes. Our goal is to study sex differences in the 3XE4 mice with AD. Blood pressure (BP, tail cuff), cognition (novel object recognition test), and cardiac function (echocardiography) were measured in both control 3XE3 (n=6) mice and 3XE4 (n=6) mice before and after Ang II (osmotic minipump, 1000 ng/kg/min). As expected, female mice weighed less than the male mice (Table). Basal BP and ejection fraction were higher in male 3XE4 mice compared to female 3XE4 mice (p<0.05). Total exploration time of novel object was significantly delayed in 3XE4 mice (p<0.05); the impairment was greater in the female 3XE4 mice. Notably, Ang II increased BP in male 3XE4 mice (151±5 mmHg) but not in female 3XE4 mice (125±2 mmHg). Unlike the 3XE3 mice, total exploration time of novel object was delayed (impaired) in both male and female 3XE4 mice at baseline and during Ang II. Although additional studies are needed to explore the underlying mechanisms, our results implicate potential sexual dimorphism in blood pressure regulation and cognition in Alzheimer’s Disease.

[Formula: see text]

Funding: NIH R01HL149677 and R21AG070188.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Motor function is not impaired in all components of the oral phase of feeding in a rat rotenone model of Parkinson’s disease
Authors: Gould Francois , Wojtas Ireneusz , Charles Nicole
Published: May 2024

Parkinson’s disease results in pathological swallowing, or dysphagia, in up to 90% of cases. Severity and extent of functional impairment of feeding is highly variable in this disease. Feeding is a multi step neuromuscular process of tightly coordinated orofacial behaviors -transport, food reduction, pharyngeal swallowing- involving multiple musculoskeletal systems — tongue, jaw muscles, hyolaryngeal muscles — innervated by multiple cranial and cervical spinal nerves. The type of food being ingested further affects this sequence. The pesticide rotenone, a type II mitochondrial inhibitor, has been epidemiologically linked to Parkinson’s disease. The goal of this project is to identify how parkinsonian neurodegeneration affects this sequence in an animal model. We hypothesize that not all elements of the sequence will be equally affected. Twelve young adult male Lewis rats received daily intraperitoneal injections of either 2.75 mg/kg of rotenone or vehicle control for 8 days. The rats were trained to eat breakfast cereal and drink water mixed with barium in front of a high speed (200 fps) videofluoroscope. From the high speed video recording duration of intraoral transport and chewing of solid food as well as lick duration for liquid drinking were measured for multiple swallows per individual on day 0 (before injection), day 1, day 4, and day 7. On day 8 animals were perfused and brains harvested, sliced, stained with immunofluorescent markers for striatal tyrosine hydroxylase to confirm effectiveness of the model. Mixed model ANOVA was used to test the hypothesis that duration of the phases varied over the course of treatment. Duration of intra oral transport changed in neither control nor rotenone treated animals (p=0.1136), but duration of chewing increased in rotenone treated rats only by day 4 (p<0.001). Duration of licks increased in liquid drinking rats from day 0. Different components of the oral feeding process vary in degree and timing of impairment in the rat rotenone model of Parkinson’s disease, with coordinated rhythmic tongue and jaw movements (licking and chewing) being most sensitive. The neurological basis for this differential sensitivity remains unclear.

Internal Rowan funds to Dr. Gould supported this work.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Impact of Aging and High-Fat Diet on Adipose Tissue-Derived Extracellular Vesicle miRNA Profiles in Mice
Authors: Cho Young-Eun , Shaoshuai Chen , Crouch Keith , Yun Joseph , Klingelhutz Aloysius
Published: May 2024

Background: Middle-aged adults show the highest obesity rates, leading to significant health complications in later years. Obesity triggers the release of altered molecules including extracellular vesicles (EVs) from excess adipose tissue (AT), contributing to various health complications. In this study, we assessed the effects of age and high-fat diet (HFD) on white AT-derived EV miRNA profiles to understand their potential roles in aging and obesity. Hypothesis: Our hypothesis is that the white AT-derived EV miRNA profiles of middle-aged mice fed HFD will demonstrate deleterious features due to the potential synergistic effects of aging and long-term HFD consumption. Method: C57BL/6 male mice were subjected to a normal chow diet (NCD) or a HFD for either 10-12 weeks (young mice, n=10) or 50-61 weeks (middle-aged mice, n=12). After evaluating metabolic characteristics, white AT-derived EV miRNAs were profiled using a NanoString miRNA panel (n=599). Results: Middle-aged mice exhibited obesity regardless of diet. Young mice fed HFD showed similar metabolic traits to middle-aged mice. In NCD group, 131 differentially expressed miRNAs (DE-miRNAs) emerged in middle-aged mice compared to young mice, including miR-21, miR-148a, and miR-29a associated with cancer, neuro/psychological disorders and reproductive diseases. In HFD group, 55 DE-miRNAs were revealed in middle-aged mice compared to young mice. These miRNAs were associated with significantly suppressed IGF1R activity. Conclusion: This study has demonstrated the altered characteristics of WAT EV miRNAs by aging and diet. Aging and diet induce significant changes in EV miRNA profiles of AT. We suggest that there might be a selective sorting mechanism of miRNAs in AT EVs, contributing to the disease progress or pathogenesis related to aging and obesity. We also suggest that AT EVs in middle-aged mice fed HFD might play a protective role in aging and obesity by inhibiting IGF1R activity.

University of Iowa College of Nursing.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
The Impact of Neonatal Curcumin Intake on Key Molecular Markers in Lipid and Glucose Metabolism
Authors: Matumba Mashudu , Mukwevho Emmanuel
Published: May 2024

The high prevalence of obesity, resulting from the increased consumption of a fructose-rich diet, poses a serious global threat to children's public health. Obesity is linked to several metabolic disorders, including insulin resistance and type-2 diabetes. Furthermore, type-2 diabetes is characterized by impaired lipid and glucose metabolism. This study investigated the impact of neonatal curcumin intake on the expression of key molecular markers related to liver lipid metabolism [Liver kinase B-1 (LKB-1), AMP-activated protein kinase (AMPK), Carnitine palmitoyltransferase-1 (CPT-1), and Acetyl-coenzyme A carboxylase-1 (ACC-1)] and glucose metabolism [serine/threonine-protein kinase (AKT-1), Glucose transporter-2 (GLUT-2), glycogen phosphorylase (GP), and Phosphoglucomutase (PGM)]. Curcumin, a polyphenolic compound derived from turmeric, is currently under extensive research for its potential therapeutic applications in various diseases. In this study, a metabolic syndrome model was induced in Sprague Dawley rats by feeding them a high fructose diet, with curcumin administered as the treatment. Gene expression was assessed through Real-Time quantitative PCR, and protein expression was analyzed using the western blot technique. The study observed that a high fructose diet led to the upregulation of genes and proteins associated with lipid metabolism, such as AMPK, LKB-1, ACC-1, and CPT-1 in liver tissues. Curcumin treatment reversed these effects, restoring normal lipid metabolism. Additionally, the high fructose diet downregulated the expression of AKT-1 in hepatic insulin signaling, which was counteracted by curcumin. Moreover, the high fructose diet increased hepatic glucose production, as indicated by the upregulation of GP and PGM gene and protein expression, while curcumin treatment suppressed hepatic glucose production by downregulating GP and PGM expression. The findings improve our understanding of curcumin's molecular mechanisms, which are not yet fully understood. They offer further evidence of curcumin's positive effects. Thus, early neonatal consumption of curcumin could be a potential strategy to prevent high fructose diet-induced obesity and related metabolic disorders, including insulin resistance and type-2 diabetes.

Lipid and Glucose Metabolism. This project was funded by the North-West University.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Effect of Inactivation of Prefrontal Cortex on Sleep-Wake States in Rat
Authors: Ponnaluri Sumegha , Groenhout Trent , Sharba Lana , Liu Tiecheng , Mashour George A. , Pal Dinesh
Published: May 2024

There is a large body of literature to support subcortical regulation of sleep-wake states, but there have been limited studies to investigate the role of cortex in sleep-wake regulation. Previously, we have demonstrated that cholinergic stimulation of prefrontal cortex can reverse general anesthesia and promote wakefulness in unanesthetized rats, and there is emerging evidence to suggest that the prefrontal cortex might be a critical node in arousal state control. To better understand the direct role of prefrontal cortex in the regulation of sleep-wake states, we quantified the effect of prefrontal cortex inactivation, via local tetrodotoxin (156 μM) infusion, on sleep architecture. Under surgical isoflurane anesthesia, adult Sprague Dawley rats (n=7 male) were instrumented with electrodes to record electroencephalogram (EEG) from frontal and parietal cortices, and electromyogram (EMG) from dorsal nuchal muscles. In addition, a bilateral guide cannula was implanted aimed at the medial prefrontal cortex for tetrodotoxin infusion. After at least a week of post-surgical recovery and conditioning to the recording chambers, rats received bilateral microinjection (500 nL) of either 156 μM tetrodotoxin or 0.9% saline (vehicle control). The tetrodotoxin and 0.9% saline infusions were performed 30-minutes before the start of lights-OFF period (8:00 pm) after which EEG and EMG data were recorded for 24h across dark and light cycles. The EEG and EMG data were manually scored (SleepSign, Kissei Comtec Inc.) in 4-second intervals into wakefulness, slow-wave sleep, and rapid eye movement sleep, and then averaged in 3h bins across 24h recording period. A linear mixed model was used to compare the changes in percent time spent in each state, mean duration per episode for each state, and mean number of episodes for each state, between the vehicle control and tetrodotoxin-infusion sessions. Inactivation of prefrontal cortex via tetrodotoxin infusion produced long-lasting statistically significant increase in slow-wave sleep (p<0.05 for 0-3h, 4-6h, 7-9h, 10-12h, 13-15, 16-18, 22-24) and decrease in wakefulness (p<0.05 for 0-3h, 4-6h, 10-12h) and rapid eye movement sleep (p<0.05 for 7-9h, 10-12h, 13-15h). These data further support a causal contribution of prefrontal cortex in regulating arousal states.

This work was supported by the National Institutes of Health (Bethesda, MD, USA) grant (R01 GM111293) to GAM and DP, and funding from the Department of Anesthesiology, University of Michigan Medical School, Ann Arbor.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Habitual Sleep and Muscle Sympathetic Nerve Activity in Humans
Authors: Bigalke Jeremy A. , Greenlund Ian M. , Tyra Alexandra T. , Bigalke Jennifer R. , Carter Jason R.
Published: May 2024

Short habitual sleep duration and inadequate sleep effciency are associated with poor cardiovascular health. Although a potential mediator of this relationship is augmented sympathetic activity, only one study to date has assessed the relationship between objectively measured habitual sleep duration and direct muscle sympathetic nerve activity (MSNA) in humans. Moreover, the proportion of resting MSNA that can be independently explained by habitual sleep while controlling for other key variables remains unknown. The purpose of the present study was to assess the independent relationship between total sleep time (TST), sleep effciency (SE), and MSNA in a large population of young males and females. We hypothesized that short TST and low SE would be associated with elevated MSNA and blood pressure. A minimum 7 days of at-home, objective actigraphy sleep monitoring was collected in 66 healthy young adults (35 males, 31 females; 24±1 years; 26±1 kg/m2). In each participant, the average of three seated brachial blood pressures was recorded and used to determine resting mean arterial blood pressure (MAP). All participants underwent an autonomic function test that simultaneously assessed heart rate (HR, electrocardiogram), beat-to-beat blood pressure (finger plethysmography) and MSNA (microneurography) during 10 minutes of quiet rest. Resting MAP (83±1 mmHg), HR (64±1 beats/min) and MSNA (19±1 bursts/min) were normally distributed. Habitual TST was significantly correlated with MSNA (r=-0.265, p=0.032), but was not associated with resting MAP (r=-0.153, p=0.219) or HR (r=-0.205, p=0.098). SE was not associated with any of the outcome variables (all p>0.25). Multiple regression was used to test the independent relationship between TST, MAP, HR, and MSNA while accounting for effects of age, sex, and body mass index (BMI). The regression model significantly predicted MAP (R2=0.253, p=0.001) and MSNA (R2=.211, p=0.005), but not HR (R2=.047, p=0.560). TST did not independently explain any additional variance in MAP (ΔR2=0.004, p=0.562) beyond that ascribed to the effects of age, sex, and BMI. In contrast, TST independently explained an additional 5% of the variance in MSNA (ΔR2=0.053, p=0.048). In a large sample of healthy young males and females, our results indicate that habitual TST explains only a minor proportion of the observed variance in resting MSNA between participants.

NIH (AA-024892).

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Does Uromodulin Play a Role in Tacrolimus-Mediated Upregulation of the Sodium Chloride Cotransporter?
Authors: Nshuti Adeline , Ume Adaku , Wenegieme Tara-Yesomi , Kamau John , Paul-Onyia Chiagozie , Williams Clintoria
Published: May 2024

Background: Tacrolimus, a calcineurin inhibitor (CNI), is a medication commonly prescribed to prevent organ transplant rejection. However, chronic CNI use has several adverse effects, including hypertension. Recent studies have revealed that the renal sodium chloride cotransporter (NCC) mediates tacrolimus-induced hypertension. However, the mechanisms underlying NCC upregulation are not fully understood. Previous studies indicate that uromodulin plays a key role in renal ion channel regulation. As such, we hypothesize that uromodulin mediates tacrolimus induced NCC upregulation. Experimental Design: To test this hypothesis, male C57BL/6 mice received tacrolimus (10 mg/kg/day) or vehicle (ethanol/DMSO/saline) for 21 consecutive days via intraperitoneal injection. The impact of tacrolimus on systolic blood pressure (BP) was monitored by tail-cuff plethysmography. To examine uromodulin and NCC expression, kidneys were harvested and processed for immunohistochemistry. Results: Compared to the BP of vehicle-treated mice (120 mm Hg ± 4.252), mice administered tacrolimus had significant increases in BP (170 mm Hg ± 3.528). Furthermore, tacrolimus treatment increased phosphorylated NCC (pNCC) and uromodulin expression. Conclusions: These results indicate that tacrolimus-induced hypertension is accompanied by pNCC and uromodulin upregulation in distal convoluted tubules. Significance: Overall, these findings highlight uromodulin as a possible regulator of NCC.

Funding: R21 DK119879, R01 DK-133698, R25DK07838.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Cerebral autoregulation metrics correlate with some major morbidity and mortality outcomes after cardiac surgery
Authors: Melvin Ryan , Godwin Ryan , Benz David , Berkowitz Dan , Mladinov Domagoj
Published: May 2024

Background: Personalized arterial blood pressure management based on cerebral autoregulation has shown clinical relevance in cardiac surgery. Here we explore the associations between lower limit of cerebral autoregulation (LLA) metrics and postoperative outcomes in a heterogenous and high-acuity population of patients undergoing high-risk cardiovascular surgery. Methods: Autoregulation parameters were determined retrospectively in 686 patients undergoing cardiac surgery at UAB Hospital. Cerebral oximetry index (COx) and hemoglobin volume reactivity index (HVx) determine a patient’s unique LLA by examining the correlation between mean arterial pressure (MAP) and near-infrared spectroscopy signals. Logistic regression analyses explored associations of area under the time-pressure curve and duration below LLA with stroke, acute kidney injury, operative mortality, low cardiac output syndrome, and mechanical ventilation lasting more than 48 hours. Any incidence of these outcomes was considered as the primary outcome of interest: major morbidity or operative mortality (MMOM). Results: We explored the association of Area under the time-pressure curve for pressures less than patient-specific Lower Limits of Autoregulation (AUCABP<LLA: and MMOM. Results are reported with odds ratio (OR) and 95% confidence intervals (CI). AUCABP<LLA was not significantly associated with MMOM incidence (HVx: Odds Ratio 1.000, 95% CI 0.970-1.030, p=0.979; COx: OR 1.006, 95% CI 0.990-1.023, p=0.456). However, for components of MMOM, specifically operative mortality (HVx: OR 1.063, 95% CI 1.013-1.115, p=0.013; COx: OR 1.027, 95% CI 1.001-1.052, p=0.038) and low cardiac output syndrome (HVx: OR 1.036, 95% CI 1.004-1.068, p=0.025), there were statistically significant relationships with AUCABP<LLA when controlling for logistic Euroscore and preoperative hemoglobin levels. Conclusions: Area under the time-pressure curve for pressures less than patient-specific LLA was not significantly associated with MMOM incidence. However, we found significant associations between components of MMOM, specifically operative mortality and low cardiac output syndrome, with an AUCABP<LLA and time under LLA. These results suggest that LLA metrics might have utility in predicting specific postoperative outcomes, but their role in predicting overall MMOM may be limited in heterogenous and high-acuity patient populations.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Increases in Central Arterial Stiffness and Reductions in Diastolic Velocity in the Large Cerebral Arteries are Associated with Age-Related Decline in Cerebral Blood Flow
Authors: Ashley John , Won Junyeon , Cardim Danilo , Tomoto Tsubasa , Zhang Rong
Published: May 2024

Background: Advanced aging is characterized by a reduction in cerebral blood flow (CBF) and an increase in central arterial stiffness. Increased central arterial stiffness results in reduced Windkessel effects and augmented pulsatile arterial blood pressure and CBF. These changes are detrimental to small cerebral blood vessels because of increases in biomechanical stresses associated with the augmented pulsatile arterial blood pressure and CBF. Purpose: To examine the associations of central arterial stiffness with cerebral hemodynamics and age-related reductions in CBF. Methods: 171 healthy subjects (20-81 yrs, 63% F) underwent color-coded duplex ultrasonography of the left and right internal carotid (ICA) and vertebral artery (VA) to characterize individual artery blood flow (BF), velocity, pulsatility, and CBF. Structural Magnetic Resonance Imaging (MRI) was used to measure total brain tissue volume (TBV). Carotid β-stiffness and carotid-femoral pulse wave velocity (cfPWV) were measured via applanation tonometry to assess central artery stiffness. Data: Age was negatively associated with global CBF (r = -0.425, p < 0.001), and positively with cfPWV (r = 0.701, p < 0.001), and carotid β-stiffness (r = 0.660, p < 0.001). Arterial stiffness was negative associated with ICA diastolic velocity (r = -0.280, p < 0.001; r = -0.259, p < 0.001) and VA diastolic velocity (r = -0.280, p < 0.001; r = -0.248, p = 0.001) controlling for sex, body mass index (BMI), education, and TBV. Carotid β-stiffness moderated indirect effect between age and CBF through ICA diastolic velocity (index of moderated-mediation -0.47 ± 0.13, [-0.74,-0.23]. cfPWV did not moderate the indirect effect between age and CBF through ICA diastolic velocity (index of moderated-mediation -0.36 ± 0.18, [-0.69, 0.03]. The indirect effect of age on CBF through VA diastolic velocity was not moderated by cfPWV (0.03 ± 0.09, [-0.13, 0.23]) or carotid β-stiffness (-0.17 ± 0.09, [-0.33, 0.01]). Conclusions: Age-related decline in CBF is mediated by the decreases in ICA blood flow diastolic velocity, and this relationship was moderated by carotid β-stiffness. This data suggests that increases in central arterial stiffness and reductions in CBF diastolic velocity in the large cerebral arteries likely plays an important role in age-related decline in CBF.

This study was supported by NIH R01HL102457-01 and NIH R01AG033106-01.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Heme Scavenging by Hemopexin Attenuates Sepsis-Induced Proinflammatory Cytokines and Kidney Insuffciency in a Humanized Mouse Model of Sickle Cell Disease
Authors: Falayi Olufunke , Williams Jada , Kumar Ravi , Afolabi Jeremiah , Adebiyi Adebowale
Published: May 2024

Sickle cell disease (SCD) is a genetic blood disorder characterized by abnormal hemoglobin production, leading to sickle-shaped red blood cells (RBC). Alteration in RBC shape results in vasoocclusion, chronic hemolysis, and multiple organ damage. One of the severe complications of SCD is an increased susceptibility to infections, including sepsis, which can be life-threatening. Kidney injury, a common and severe complication of sepsis, contributes to the complexity and poor outcomes associated with morbidity and mortality in SCD. However, the mechanisms that underlie septic acute kidney injury (AKI) in SCD are poorly understood. Here, we examined the effects of sepsis in transgenic homozygous SCD (SS; Townes model) mice and their non-sickling (AA) counterparts. We tested the hypothesis that aggravation of inflammation and oxidative stress by free heme released during hemolysis contribute to sepsis-induced kidney insuffciency in SCD. AA and SS mice were subjected to 18 h of sham operation and cecal ligation and puncture (CLP), a pre-clinical model of polymicrobial sepsis, after which kidney function was evaluated by transdermal measurement of glomerular filtration rate (GFR). AKI biomarkers, renal oxidative stress, and cytokines levels were also investigated. We demonstrate that mid- to high-grade CLP (ligation of 60-75% of the cecum and multiple punctures with 21-gauge needles) caused 100% mortality in SS mice. Unlike AA mice (100% survival), SS mice subjected to low-grade CLP (LgCLP; ligation of <45% of the cecum and a single puncture with 21-gauge needles) exhibited 40% survival. LgCLP reduced body weight but did not exacerbate splenomegaly in SS mice. Basal plasma bilirubin, heme, and ferritin were significantly higher in SS than in AA mice. In contrast to AA, LgCLP amplified the increase in plasma bilirubin, heme, and ferritin in SS mice. LgCLP also decreased GFR and increased renal oxidative stress, AKI biomarkers, and kidney-to-body weight ratio in SS mice. Luminex multiplex cytokine analysis indicated that the plasma levels of multiple pro-inflammatory cytokines were elevated in septic SS mice. Heme scavenger hemopexin (HX) diminished LgCLP-induced plasma heme increase. HX also mitigated kidney insuffciency, inflammation, and mortality in the septic SS mice. Our findings suggest that free heme contributes to septic AKI in SCD mice and that HX therapy may attenuate the harmful effect of heme in SCD during sepsis.

NHLBI: R01 HL151735.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Mechanisms of PAK1-Induced Skeletal Muscle Myokines in Improving Islet β-Cell Function
Authors: Balakrishnan Rekha , Kebrom Leah , Veluthakal Rajakrishnan , Thurmond Debbie
Published: May 2024

The critical role of skeletal muscle in regulating metabolic homeostasis is well-acknowledged. The p21-activated kinase (PAK1), a prominent signaling molecule in skeletal muscle, has garnered attention for its potential modulatory role in glucose and mitochondrial metabolism. By applying conditioned media derived from PAK1-enriched L6 Glut4 myc myotubes or myoblasts to INS-1 832/13 clonal β-cells, we confirmed that a muscle-derived circulating factor(s) could enhance β-cell function. Furthermore, our mass spectrometry analysis in the conditioned media (CM) collected from PAK1 enriched L6.GLUT4myc myotubes revealed elevated levels of one protein in particular, hepatocyte growth factor activator (HGFAC), which is categorized as a secreted myokine. HGFAC is secreted into the circulation, where, upon activation, it can act in a paracrine or endocrine fashion to proteolytically cleave and activate HGF. It has been reported that HGF has a vital role in islet β-cell mass and function and HNFα, a transcription factor that is expressed in pancreatic β-cells regulates β-cell mass or function by modulating HGFAC expression. Thus, we hypothesize that PAK1-enriched skeletal muscle releases HGFAC into the serum-free conditioned medium and the medium carrying HGFAC when applied to islet β-cells enhances insulin secretion. Elevated levels of HGFAC protein were detected in the cells and their associated CM from PAK1-enriched skeletal myotubes, as compared with that of GFP-transduced control myotubes, using sandwich ELISA to quantify HGFAC. Notably, these cells were incubated in a serum-free medium, a means to eliminate serum factors that might impact HGFAC levels or detection capacity. Given this, we tested the effect of this serum-free CM collected from PAK1-enriched L6.GLUT4myc myotubes application to species-matched (rat) clonal β-cells functional capacity. Indeed, CM from PAK1-enriched myotubes significantly enhanced glucose-stimulated insulin secretion (GSIS), as compared that of the control CM. The presence of elevated HGFAC levels in PAK1-enriched cells, and the beneficial impact of this HGFAC-enriched CM upon beta cell function, reveals a new mechanism by which PAK1-enrichment in skeletal muscle imparts improved overall whole-body glucose homeostasis. further hints at a possible intricate relationship between muscle-pancreas crosstalk in the regulation of islet β-cell insulin secretion. Future investigations into possible autocrine functions of PAK1-enriched skeletal muscle are underway.

This research was funded by the National Institutes of Health to D.C.T. (DK067912, DK112917, and DK102233), and an American Heart Association Postdoctoral fellowship to R.B. (#905770).

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
The Dynamic Genome at Altitude: Mitochondrial DNA Copy Numbers in Acute and Chronic Hypoxia
Authors: Janocha Allison , Novotny Michael , Xu Weiling , Chen Ruoying , Hu Bo , Koch Carl , Tiso Mauro
Published: May 2024

Mitochondria contain a tiny circular DNA (mtDNA) that encodes components of the electron transport chain, including Complex IV, where over 95% of oxygen is consumed in the process of generating energy. Each mitochondrion contains tens to hundreds of copies of mtDNA, which decrease with aging and disease, but little is known regarding how mtDNA levels change in response to hypoxia. Here we compare samples with different durations and magnitudes of exposure to high-altitude hypoxia: Ethiopian Amhara with >5000 years exposure and the potential for evolved adaptations, Ethiopian Oromo with ~500 years of generations of lifelong acclimatization, and acutely exposed European trekkers with 15 days of abrupt individual acclimatization followed by descent to baseline. Lowland natives of the same ethnicities provide unstressed reference samples. Our previous studies found that Amhara adapted to hypoxia through increased blood flow due to nitric oxide-mediated vasodilation, while Oromo have increased carrying capacity through elevated hemoglobin concentration. We measured mtDNA copy numbers relative to nuclear DNA (mtDNA-CN) in 326 healthy adults: 52 low-altitude Amhara at 1200 m, 113 high-altitude Amhara at 3700 m; 47 low-altitude Oromo at 1700 m, and 105 high-altitude Oromo at 4000 m; and 9 European lowlanders at a baseline of 1300 m, after ascent to 5050 m, and upon return to 1300 m. High-altitude Amhara had 21% higher median mtDNA-CN than their low-altitude counterparts (median (IQR): high-altitude, 363.0 (281.0–427.0); low-altitude, 299.0 (246.1–333.2); p<0.0001), while high-altitude Oromo had 17% lower mtDNA-CN than their low-altitude counterparts (high-altitude, 236.7 (165.2–315.6); low-altitude, 283.7 (216.9–335.6); p=0.01). High-altitude Amhara had significantly higher median mtDNA-CN than high-altitude Oromo (p<.0001). European lowlanders had 44% lower mtDNA-CN after an 13-day ascent to 5050 m (1300 m, 322.5 (262.8–356.4); 5050 m 180.9 (145.1–230.5); p=0.002) that returned to baseline (319.5 (247.3–267.6); p=0.5) after a 6-day descent to 1300 m. These findings further confirm variation in acute and chronic responses to hypoxia, within and across populations. These findings require validation and expansion to address the mechanisms connecting expression of mtDNA copy numbers to oxygen-requiring bioenergetics.

This work is supported by the National Heart, Lung, and Blood Institute HL060917 and National Science Foundation BCS-0452326.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Effect of Endothelin-1 on Resting Blood Pressure and the Blood Pressure Response to Hypoxia in Healthy Young Men
Authors: Gonsalves Anna , Baker Sarah , Jacob Dain , Harper Jennifer , Manrique-Acevedo Camila , Limberg Jacqueline
Published: May 2024

Objectives: Upregulation of endothelin-1 (ET-1) and its receptors have been linked to increases in hypoxic sensitivity of the carotid chemoreceptors and the development of hypertension. As such, chemoreflex sensitization has been shown in pre-clinical models to be attenuated by ET-1 receptor blockade. Herein, we sought to assess a role for ET-1 in the maintenance of resting blood pressure (BP) in healthy young men and determine whether chemoreflex control of BP could be altered by ET-1 blockade. We hypothesized endothelin receptor antagonism with oral bosentan would lower resting BP in healthy young men as well as the acute BP response to hypoxia. Methods: Twenty-four healthy young men (31±5 yrs, 26±3 kg/m2) completed two study visits (control, bosentan) separated by a minimum of 1 week. The nonspecific endothelin receptor antagonist bosentan (62.5 mg) was taken by mouth twice daily for 3 days prior to the second study visit. On each visit, beat-by-beat BP was assessed under 3 inspiratory air conditions: 1) steady-state normoxia (FiO2 0.21), 2) chemoreflex excitation produced by acute, graded hypoxia (FiO2 0.05 – 0.21), 3) chemoreflex inhibition elicited by transient hyperoxia (FiO2 1.00). Results: Oral bosentan treatment resulted in an increase in plasma ET-1 (0.9±0.9 to 1.3±0.6 pg/mL, p=0.004), supporting receptor blockade. Resting diastolic and mean BP were reduced following 3 days of bosentan treatment compared to control (diastolic: 73±5 to 69±7 mmHg, p=0.007; mean: 93±7 to 88±7 mmHg, p=0.005) with no change in systolic BP (p=0.507). Notably, the BP response to both acute hypoxia (-0.48±0.38 to -0.25±0.31 mmHg/%, p=0.004) and hyperoxia (main effect of bosentan, p=0.025) were attenuated following bosentan. Conclusions: Acute oral bosentan treatment resulted in a reduction in resting BP in healthy young men. The effect of endothelin receptor inhibition with bosentan further attenuated the rise in BP during chemoreflex excitation via acute, graded hypoxia as well as the fall in BP during chemoreflex inhibition (transient hyperoxia). Together these data support a role for ET-1 in control of resting BP in healthy young men, possibly through a chemoreceptor-mediated mechanism.

NIH HL130339 (JL), Mayo Clinic Center for Biomedical Discovery (JL, SB).

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Limb Position Influences Peripheral Arterial Stiffness Reduction with Reactive Hyperemia
Authors: Jackson Ronald E. , Lima Natalia S. , Sherman Sara R. , Hibner Brooks A. , Clifford Philip S.
Published: May 2024

Reactive hyperemia can acutely reduce peripheral arterial stiffness. The reduction in peripheral arterial stiffness with reactive hyperemia has been suggested to be flow dependent. However, no previous studies have manipulated the magnitude of hyperemia. We manipulated blood flow by altering limb position to test the hypothesis that a larger increase in blood flow would lead to a greater reduction in peripheral arterial stiffness. Fourteen healthy young adults (5 women; age: 25 ± 5 years; mean ± SD) were included in this study. Peripheral arterial stiffness assessed via brachial to radial pulse wave velocity (PWV) was measured by placing pulse tonometers simultaneously over the brachial and radial arteries. Doppler ultrasound was used to measure brachial arterial blood flow. Arterial blood pressure was continuously monitored via photoplethysmography on the middle finger of the contralateral hand. Reactive hyperemia was performed with the right arm positioned below (≍50°) and above (≍50°) heart level using a rapid-release cuff positioned on the upper arm, inflated to 220 mmHg, sustained for 5 min, then released. Measurements were recorded before cuff inflation and at 5, 15, and 30 min after cuff release. Repeated measures ANOVA revealed a significant condition effect (p<0.01) with peripheral PWV higher with the arm below the heart. There was a significant time x condition interaction (p<.05). At 5-min after reactive hyperemia, peripheral PWV was reduced more with the arm below the heart (9.58 ±1.65 to 7.26 ± 1.51 m/sec) than above the heart (7.08 ± 1.79 to 5.88 ± 1.43 m/sec). Mean arterial pressure did not change across time points (p>0.05). Peak brachial artery blood flow was greater with the arm below the heart (477.37 ± 145 vs 368.64 ± 137 ml/min; p<.001). The results show that reactive hyperemia produces an acute reduction in brachial to radial PWV. The reduction in peripheral arterial stiffness was greater when the arm was below the heart. The mechanism for position-related differences in the reduction in peripheral arterial stiffness with reactive hyperemia may be associated with the magnitude of increase in blood flow.

REJ was supported by National Heart, Lung, and Blood Institute (5T32HL134634-04).

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
A novel target for attenuating T1DM-induced myocardial ferroptosis
Authors: Gawargi Flobater I. , Mishra Paras K.
Published: May 2024

Background: The DMCM-AHEAD trial showed that lipotoxicity is a distinct feature of diabetic heart failure, which initiates and exacerbates cardiac pathogenesis in diabetic patients. Circulating iron levels are increased in diabetic patients. The combined presence of lipids and iron suggests a predominant role of ferroptosis in diabetes-induced heart failure. However, molecular targets for diabetes-induced myocardial ferroptosis remain unclear. In the T1DM heart, matrix metalloproteinase-9 (MMP9), a protease, is upregulated, and targeted deletion of MMP9 is cardioprotective. Hypothesis: Targeted deletion of MMP9 mitigates T1DM-induced myocardial ferroptosis. Methods and results: We performed in vitro studies on the loss and gain-of-function of MMP9 using human cardiomyocytes (AC16 cells). Overexpression of MMP9 downregulates (-1.55-fold p<0.001) GPX4, a key marker of ferroptosis, while inhibition of MMP9 upregulates (+2.03-fold p<0.001) GPX4 (n=6), suggesting a key role of MMP9 in GPX4 regulation and ferroptosis signaling. To determine the specific role of MMP9 in T1DM-induced ferroptosis, we evaluated ferroptosis markers in the heart (LV) tissue of male Insulin2 mutant (Ins2+/-) Akita (T1DM), littermate euglycemic Ins2+/+ WT, Akita/MMP9 knockout (MMP9KO), and MMP9KO mice (n=3-6). The cardiac levels of Acyl-CoA synthetase long-chain family member-4 (ASCL4), which initiates the formation of lipid peroxides, and divalent metal transporter-1 (DMT1), which increases redox-active iron, were upregulated in the Akita while downregulated in the Akita/MMP9KO hearts (Akita vs WT: ASCL4: +1.42-fold p<0.05, DMT1: +1.34-fold p<0.05; Akita/MMP9 vs Akita: ACSL4: -1.46-fold p<0.05, DMT1: -1.03-fold p<0.05). Furthermore, cardiac levels of Ferritin-Light Chain (FLC), which stores iron to suppress ferroptosis, was downregulated in the Akita but upregulated in the Akita/MMP9KO hearts (Akita vs WT: -2.01-fold p<0.01, Akita/MMP9 vs Akita: +1.36-fold p<0.05). These results suggest that upregulation of MMP9 promotes while inhibition of MMP9 mitigates ferroptosis in the T1DM heart. Conclusion: This is the first report to reveal MMP9 as a promising therapeutic target for T1DM-induced myocardial ferroptosis.

This work was supported in part by the National Institutes of Health (NIH) Grant R56HL156806 to PKM, and University of Nebraska Medical Center (UNMC) Presidential Graduate Fellowship to FIG.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Physical activity mitigates serotonin and oxidative stress-associated mesenteric arterial endothelial dysfunction in obesity
Authors: Lee Junghoon , Lee Jonghae , Park Yoonjung
Published: May 2024

Introduction: Serotonin (5-HT) signaling may play a role in modulating vascular endothelial function. Obesity-induced oxidative stress causes the development of cardiovascular disease (CVD). We aimed to investigate the protective effect of voluntary wheel running (EX) on serotonin receptor (5-HT1B) and oxidative stress in the mesenteric artery of obese mice. Methods: Mice were randomly divided into four groups. They were fed a control low-fat diet (LF) or high-fat diet (HF; 45% of calories from fat) and provided with voluntary wheel running (LF-EX or HF-EX) or a sedentary condition. The protein expressions of phosphorylated-endothelial nitric oxide synthase (p-eNOS), 5-HT1B receptor, Akt, and proteins regulating oxidative stress were quantified by Western blot analysis. Statistical comparisons between groups were performed with two-way ANOVA with Fisher’s LSD test. Results: The protein expressions of p-eNOS, 5-HT1B receptor, and p-Akt in HF were lower compared to LF, but EX increased the protein levels ( P < 0.05). NOX2 in HF was higher compared to LF, but EX decreased it ( P < 0.05). SOD1, SOD2, and UCP2 in HF were lower compared to LF, but EX increased the protein levels ( P < 0.05). There was no difference in expressions of Akt, Gαq/11, NOX4, and VDUP1 between groups. Conclusion: Voluntary wheel running improves e-NOS-mediated vascular endothelial function possibly via increased 5-HT1B receptors and reduced oxidative stress, which could mitigate the risk of obesity-induced CVD.

This study was supported by grants from the Cardiovascular Research Foundation Asia (#16215 to Y. P.) and the University of Houston (Small Grant Program to Y. P.).

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.
Local Activation of Angiotensin II Type 2 Receptors Improves Microvascular Endothelial Function in Healthy Women With a History Preeclampsia
Authors: Schwartz Kelsey , Jalal Diana , Santillan Mark , Stanhewicz Anna
Published: May 2024

Women who had preeclampsia (hxPE) have a >4-fold risk for developing cardiovascular disease (CVD) compared to women who had an uncomplicated pregnancy (hxHC). These women demonstrate attenuated vascular endothelium- and nitric oxide (NO)-dependent dilation, secondary to exaggerated angiotensin (ang) II-mediated constriction, following pregnancy but before the onset of CVD. Despite the known dysregulation of ang II-mediated responses postpartum, the role of vasodilatory ang II type 2 receptors (AT2R) in this dysfunction is unknown. We hypothesized that, compared to hxHC, hxPE would have reduced AT2R-mediated dilation and reduced AT2R expression in primary biopsied endothelial cells. We further hypothesized that endothelium- and NO-dependent dilation would be attenuated in hxPE, and that local AT2R activation would improve these responses in hxPE. Nine hxPE (34±7 years, 25±14 months postpartum) and 9 hxHC (35±3 years, 32±12 months postpartum) had 4 intradermal microdialysis fibers placed in the ventral forearm. Sites 1-2 received graded infusions of compound 21 (C21, AT2R agonist; 10−14-10−3mol/L) alone or with L-NAME (NO-synthase inhibitor; 15mM). Sites 3-4 received lactated Ringer’s (control) or 10−11M C21 and underwent a standard local heating (LH) protocol (42°C; 0.1°C·s−1) to assess endothelium-dependent dilation. After full expression of the LH response, 15mM L-NAME was perfused to assess NO-dependent dilation. Red cell flux was measured over each site with laser-Doppler flowmetry. Cutaneous vascular conductance was calculated (CVC=flux/mean arterial pressure) and normalized to maximum (%CVCmax; 28mM SNP+43°C). AT2R protein expression in biopsied venous endothelial cells (n=4/group) was quantified using immunofluorescence. AT2R-mediated dilation (31±8 vs. hxHC: 95±25%CVCmax, p=0.01) and the NO-dependent portion of this response (21±9 vs. hxHC: 64±23%, p=0.04) was reduced in hxPE. AT2R expression in biopsied endothelial cells was attenuated in hxPE (0.59±0.10 vs. hxHC: 0.79±0.07 arbitrary units; p=0.008). hxPE had attenuated endothelium- (79±7 vs. hxHC: 94±9%CVCmax, p<0.001) and NO-dependent dilation (55±11 vs. hxHC: 71±13%; p=0.01) responses to LH. Local AT2R activation augmented endothelium- (92±11%CVCmax vs. control; p=0.02) and NO-dependent (78±12% vs. control; p<0.001) dilation in hxPE but had no effect in hxHC (all p>0.05). These data suggest that reductions in AT2R-mediated dilation and expression contribute to attenuated endothelial function after preeclampsia. Furthermore, AT2R activation may improve endothelial function through NO-dependent mechanisms in women who have had preeclampsia before the onset of CVD.

Internal Funds.

This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.