bluuebunny/crossref_metadata_2025 huggingface dataset:
Cerebrovascular Compliance during Progressive Hypotension in Patients with Autonomic Failure
Authors: Sajid Aleena , Shoemaker Leena , Schondorf Ronald , Shoemaker Kevin
Published: May 2024

Background: Cerebral perfusion during reductions in arterial pressure (AP) can be supported transiently by a Windkessel mechanism that increases cerebrovascular compliance (Ci). This defense mechanism exists in healthy participants during rapid standing and in patients during vasovagal syncope. However, it remains unknown whether the rise in Ci with falling AP exhibits a threshold effect. Thus, we tested the hypothesis that increased Ci is passive to a reduction in AP and starts to increase only after a threshold has been reached. To test this hypothesis, it was necessary to study a population that tolerates progressive large reductions in BP without a loss of consciousness. Therefore, we analyzed Ci changes during a graded head-up tilt (HUT) from patients with autonomic failure (AF). Methods: Finger AP and right middle cerebral artery blood velocity (MCAv) were recorded from 5 AF patients (n = 5 male, 61 ± 23 years, 25 ± 5 kg/m2) at supine rest and during graded-HUT (30, 45, 60 degrees). Tilt gradients increased incrementally every 5 minutes until AP reached a critically low value prompting termination of HUT. The total time in HUT was 11 ± 4 min. Individual AP and MCAv waveforms during supine rest and graded HUT (one waveform every 5 s) were assessed with a modified Windkessel model to calculate Ci and cerebrovascular resistance (CVR). Pulse pressure (PP) was calculated as systolic AP − diastolic AP. A threshold value for the increase in Ci was determined as five consecutive cardiac cycles greater than the average supine Ci plus 2 standard deviations. Results: Graded HUT resulted in an overall reduction in AP (85 ± 18 to 50 ± 7 mmHg), PP (72 ± 22 to 32 ± 19 mmHg), mean MCAv (62 ± 12 to 35 ± 7 cm/s), and CVR (1.4 ± 0.1 to 1.0 ± 0.3 mmHg/cm/s; all p < 0.05 vs supine). Ci increased by 905 ± 756% (p = 0.04 vs supine). The threshold effect was evident as Ci began to increase progressively after PP fell by 15 ± 3 mmHg and AP fell by 12 ± 2 mmHg. Conclusions: Our results provide evidence that Ci increases after a threshold reduction in PP and AP in the apparent absence of autonomic support. These data support the idea that increasing Ci during reductions in AP represents a pressure-dependent Windkessel mechanism. Of interest, our findings provide clinical insight into how AF patients compensate for such large reductions in pressure without the assistance of CVR as a defense mechanism.

NSERC USRA — Western University, Natural Sciences and Engineering Research Council of Canada (NSERC, Grant No. RGPIN-2018-06255).

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.
Dietary Effect on Peripheral and Cerebral Vascular Function in Adults with Non-Alcoholic Fatty Liver Disease
Authors: Wang Tianyu , Chen Lin-Sheng , Gallagher Isabelle , Li Yanrong , Caillaud Marie , Park Jessica , Alhalimi Taha
Published: May 2024

Objective: Non-alcoholic fatty liver disease (NAFLD) is a recognized independent risk factor for cardiovascular and cerebrovascular dysfunction. The present study evaluated the effect of dietary interventions on peripheral and cerebral vascular function in individuals with NAFLD. Methods: We studied 30 middle-aged adults (55±9 years) with NAFLD or with elevated NAFLD risk (with prediabetes symptoms). Liver fat content was assessed via 1H magnetic resonance spectroscopy. NAFLD was defined as liver fat proton density fat fraction (PDFF) exceeding 5%. Participants were randomly assigned to a low-carbohydrate diet (carbohydrate intake <30 g/d) or a low-calorie diet (30% calorie intake reduction). Arterial stiffness (via brachial-ankle pulse wave velocity-baPWV), carotid artery intima-media thickness (IMT), endothelium-dependent vasodilation (via flow-mediated dilation-FMD), cerebrovascular reactivity (CVR) in the middle cerebral artery (MCA), and blood concentrations of cardiovascular risk factors were measured before and after a two-week dietary intervention. Results: Participants with NAFLD represented 70% of the current cohort. Following the dietary interventions, participants had significant reductions in body weight (95%CI [-3.22, -1.41 kg]) and fat mass (95%CI [-1.64, -0.56 kg]), accompanied by decreased liver fat content (95%CI [-2.62, -0.79%]). These changes were only evident in the NAFLD group with no significant differences between the two dietary interventions. Systolic and diastolic blood pressure as well as pulse pressure significantly decreased in both NAFLD and non-NAFLD groups. Total cholesterol (95%CI [-22.2, -1.5 mg/dL]) and triglyceride (95%CI [-30.4, -0.9 mg/dL]) concentrations decreased in those with NAFLD assigned to the low-carbohydrate diet. baPWV decreased (95%CI [-78.6, -12.4 cm/s]) only in individuals with NAFLD assigned to the low-calorie diet. FMD significantly increased (95%CI [0.5, 5.1%]) only in individuals with NAFLD assigned to the low-carbohydrate diet. Lower baseline liver fat content was associated with greater improvement in FMD (r=-0.60, p=0.008) in the NAFLD group. Carotid IMT and cerebrovascular parameters (e.g., pulsatility index, CVR, MCA blood flow velocity) remained unchanged in any groups. Changes in vascular function were not associated with the corresponding changes in liver fat content. Conclusion: The two-week dietary intervention involving either a low-carbohydrate or low-calorie diet elicited significant reductions in liver fat content and improvements in peripheral arterial stiffness and endothelium-dependent vasodilation in adults with NAFLD.

UT Aging Initiatives.

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.
Little Brown Bats and White Nose Syndrome: Predicting Colony Outcomes from Cytokine Biomarkers
Authors: Gerber Belle , Klink Amy C , Hindle Allyson G , Richardson Christopher S
Published: May 2024

White Nose syndrome (WNS) is the disease caused by a fungal pathogen, Pseudogymnoascus destructans ( Pd) that has been decimating 13 species of North American bat populations since 2006. Little brown bats, Myotis lucifugus, are severely threatened by this pathogen with population declines over ninety percent in some colonies after exposure to the fungus. Because immune function is suppressed during hibernation, this disease is able to ravage bats throughout the winter. Pathogen surveillance is an essential component of studying and managing WNS in North American bats. As part of a larger study on predicting how maternity colonies are recovering from WNS, we aim to validate and calibrate a suite of biomarkers to better understand the health of individual bats within colonies that are currently affected or recovering from Pd, which can help predict disease occurrence and prevalence. One set of biomarkers is the host individual’s inflammation responses, measured by mRNA expression of cytokines known to respond to Pd infection in Myotis ( IL-6, IL-17ɑ, IL-1). This study compares host cytokine expression across 8 colonies with varied exposure to the Pd pathogen from a non-invasively collected sample (guano, n=355 bats) and a minimally invasive biosample (wing biopsy, n=33 paired samples). Host mRNA isolated from guano represents a non-invasive but also indirect metric of host health, and cytokine mRNA could be detected in 353 of 369 samples from Myotis guano. Significant differences in the relative expression of IL-17a (F7,275=2.494, p=0.017) and IL-1B (F7,288=2.278, p=0.03), but not IL-6 (F7,293=1.166, p=0.322), were detected among colonies in the guano samples using one-way ANOVA. This comparison will help in the development of a non-invasive colony assessment tool using known disease state and fungal load to assess the likelihood of colony recovery.

Funded by the US Fish and Wildlife Service.

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.
Knockout of DEPDC5, the gene associated with drug-resistant focal temporal epilepsy, causes abnormal Ca2+-waves in human iPS cell-induced neurons
Authors: Horiuchi Yuna , Inaba Haruka , Hando Tetsuya , Ai Tomohiko , Miida Takashi
Published: May 2024

Genetic variants in the DEP domain containing 5 (DEPDC5) are one of the most common causes of inheritable drug-resistant temporal focal epilepsy. Epilepsies caused by DEPDC5 variants are often associated with brain malformations and sudden unexplained death in epilepsy (SUDEP). It has been reported that the DEPDC5 genes regulates cell growth via rapamycin complex 1 (mTORC1) pathways. Though several animal models showed knockout of the DEPDC5 causes epilepsy, the underlying mechanism(s) by which DEPDC5 variants cause neuronal excitations remains unelucidated in human cells. To examine whether knockout of DEPDC5 causes abnormal excitations in human iPS cell (iPSC)-induced neurons, DEPDC5 was knocked out using CRISPR-Cas9 gene editing methods. Expression of DEPDC5 peptides was confirmed by a mass spectroscopy. Then, the cells were differentiated into neurons by Dual Smad Inhibition. Spontaneous cellular excitation was evaluated by Ca2+-imaging (AquaCosmos/Ratio imaging system, Hamamatsu Photonics). DNA sequencing of the DEPDC5-knockout cells showed a truncated change, c.251_258delCTTTGGGG:(p.Gly15Glyfs*5), in one allele. The DEPDC5 peptides encoded by exon 7 were decreased to less than half in the DEPDC5-knockout cells compared to the wild type (WT) cells. Ca2+-imaging showed abnormal Ca2+ bursts in neurons derived from the DEPDC5-knockout cells, while the WT cells did not show any abnormal Ca2+ waves. These results indicate that haploinsuffciency of DEPDC5 can cause abnormal excitation in human iPSC-induced neurons. Currently, we are planning to further investigate cellular excitations in iPSC-induced cardiomyocytes to dissect underlying mechanisms of SUDEP.

This work was supported in part by a Grant-in-Aid for Scientific Research (C) [grant number 18K08900 and 21K08135 (to T.A.)] and a Grant-in-Aid for Young Scientists [grant number 22K15694 (to Y.H.)] from the Japan Society for the Promotion of Science.

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.
Sarcoplasmic reticulum (SR)-mitochondria tethering is lost in human heart failure
Authors: Latchman Nadina , Margulies Ken , Prosser Ben , Elrod John
Published: May 2024

Sarcoplasmic reticulum (SR)-mitochondria (SR-mito) tethering facilitates communication between these organelles and regulates many physiological processes critical for cardiomyocyte function. Recent evidence suggests that alterations in SR-mito tethering impacts cardiac metabolism and calcium handling which contributes to cardiovascular pathologies, such as heart failure (HF). To characterize SR-mito apposition in cardiac disease we obtained electron microscopy (EM) images of individual cardiomyocytes freshly isolated from failing hearts explanted from ischemic (ICM), ischemic-dilated (ICM-DCM) and dilated cardiomyopathy (DCM) patients undergoing transplantation and nonfailing control hearts. Topographical EM analysis revealed a significant increase in the mean SR-Mito distance, as well as an increase in the minimum SR-mito distance (closest approximation of any single mitochondrion to SR) in ICM, ICM-DCM and DCM cardiomyocytes, compared to nonfailing controls. Results from the EM analysis also revealed that in DCM there was a decrease in mean mitochondrion perimeter in contact with the SR, as well as a decrease in SR in approximation with mitochondria at a distance <50-nm. In agreement, nonfailing hearts had a greater length of outer mitochondrial membrane in close contact (<20-nM) with the SR, as compared to failing cardiomyocytes. ICM and DCM cardiomyocytes displayed an overall reduction in mitochondrion perimeter and circularity, suggesting smaller and more fragmented mitochondria. Surprisingly, failing cardiomyocytes exhibited an overall increase in mitochondrial area compared to nonfailing controls. To define the molecular changes that may underlie loss of SR-mito tethering, we evaluated the expression of several proposed linkers. qPCR analysis of left ventricular samples revealed that mRNA expression of mitofusin 2 is significantly decreased in both hypertrophic cardiomyopathy (HCM) and DCM. Further, other proposed tethering components including FUNDC1, BAP31, DJ-1 and VAPB demonstrated decreased mRNA expression in HCM, DCM and ischemic HF samples, compared to nonfailing controls. IP3R1 displayed increased mRNA expression in HCM and DCM human HF samples, whereas IP3R2 and VDAC1 displayed increases in expression in HCM and ICM. These results highlight that transcriptional remodeling of the components mediating SR-mito tethering and communication may contribute to the observed structural changes in inter-organelle approximation in cardiomyocytes. These studies provide rationale for causal interrogation of the structural mechanisms regulating SR-mito communication in the context of HF progression.

Fellowship in Biomedical Sciences, Lewis Katz School of Medicine.

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.
Oxidative stress: A driving force in CKD induced heart failure
Authors: Sen Payel , Hamers Jules , Sittig Theresa , Zhang Hengliang , Zandbergen Lotte , Merkus Daphne
Published: May 2024

Background: Several clinical investigations have shown that individuals with renal impairment are more likely to experience heart failure. Cardiac remodeling happens relatively early in the course of kidney injury, yet research into identification of common markers of cardiorenal signaling remains insuffcient. This may be because studies conducted in small animal models do not accurately reflect the complexity of the disease. To bridge the translational gap, we developed a swine model for chronic kidney disease (CKD) Aim: We employed proteome studies to clarify the pathophysiological impact of chronic kidney disease (CKD) on the heart and correlate to cardiac function and perfusion in order to offer mechanistic insights. Methods: We used microspheres to embolise both kidneys of swine at 10-12 weeks of age while sham operated swine served as controls. Post 6 months, we performed pressure volume loops to assess cardiac function, while coronary flow reserve (CFR) was measured by intracoronary infusion of adenosine in control and CKD. (LC-MS-MS based proteomic analyses of left ventricular tissue was performed. Paraffn embedded myocardium and kidney tissues were histologically examined for interstitial fibrosis and oxidative stress. Results: Renal embolization resulted in mild chronic kidney injury as evidenced by increased fibrosis staining and urinary NGAL (24±4 vs 48±9 pg/ml). Hemodynamic parameters showed increased wall stress (20±3 vs 40±7 ml*mmHg/g) as well as increase of end diastolic volume (1.5±0.1 vs 1.9±0.1 ml/kg) indicating dilation of the left ventricle in CKD. Quantitative proteomic analysis detected significant differences in the left ventricle of the controls when compared to those with CKD and STRING pre-ranked functional analysis showed enrichments in pathways related to reactive oxygen species. Furthermore, we detected alterations of pathways associated with remodeling of the extracellular matrix (ECM), Oxidative stress and ECM remodeling were confirmed histologically. Interestingly, in CKD we found that mitochondrial proteins like cytochrome oxidase (MT-CO2) and ATP5 synthase subunit were downregulated suggesting mitochondrial dysfunction which was associated with higher basal coronary blood flow (0.48±0.05 vs 0.87±0.11 ml/min/g). Conclusions: Our proteomic data in swine model provides strong evidence that mild CKD can induce early alterations in mitochondrial function along with oxidative stress and ECM remodeling. Thus, we aim to further our understanding by applying our proteomic findings in conjunction with functional hemodynamic data in this swine model of cardiorenal disease.

German Center for Cardiovascular Research (DZHK81Z0600207 to D.M. and P.S.).

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.
Lumbar epidural electrical stimulation enhances respiration in mice
Authors: Huang Ruyi , Yamamoto Mark T , Zhou Yan , Jin Benita , Bao Yunrui , Masari Tamara , Zhao Yimeng
Published: May 2024

Spinal cord epidural electrical stimulation (EES) has emerged as a novel approach to modulate and interrogate the neural circuit(s) underlying sensorimotor functions in the past few decades. Recent studies have revealed that cervical EES can regulate respiration in both human subjects and animal models. Furthermore, coupled cervical and lumbar stimulations significantly increased the rhythmic motor outputs in both the cervical and lumbar spinal cord. We hypothesize that the lumbar and cervical coupling is underpinned by cervico-lumbar synaptic connections, and thus, EES at level of the lumbar spinal cord alone may also facilitate respiration via the cervico-lumbar circuit. In this study, we applied EES to the dorsal surface of the lumbar spinal cord between levels 1 and 6 (L1-6) in anesthetized mice. We found that rostral lumbar (L1-2) EES at a stimulation intensity of 0.5 mA elicited significantly higher respiratory frequency, tidal volume, and minute ventilation responses compared to the other lumbar levels (L3-4 and L5-6) tested at intensities ranging from 0.1-1.0 mA. The increased respiratory activity elicited by lumbar stimulation persisted even after the stimulation ceased. Using the optimal stimulation parameters that we identified, we further investigated the underlying mechanism of the lumbar EES-induced respiratory response by examining the neuronal activation patterns. Using immunostaining, we detected c-fos signals, a marker of neuronal activity, in the cervical spinal cord and brainstem after EES at L1-2 using 0.5 mA at 30Hz. This indicates that focal lumbar stimulation elicits remote neuronal activation in cervical spinal cord and brainstem, regions that contain respiration-related neural circuits. These findings suggest that lumbar EES may facilitate respiration by recruiting paraspinal respiratory circuits and potentially supra-spinal respiratory central pattern generator(s). This study provides insights into the development of novel approaches to restore normal respiratory patterns for patients with respiratory disorders, particularly spinal cord injuries.

This work was supported by The Louis and Harold Price Foundation, H & H Evergreen Foundation, Jonathan and Susan Dolgen Foundation, the National Institute of Drug Abuse (R01DA047637), and the National Institute of Neurological Disorders and Stroke (UH3NS119772) in the National Institutes of Health.

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.
Investigating the Effect of Rapamycin on Impaired Proteostasis in Aged Skeletal Muscle After Disuse Atrophy
Authors: Fuqua Jordan , Brecheen Parker , Miller Benjamin
Published: May 2024

Older individuals undergo loss of muscle mass and strength, which can be compounded during bed rest and extended hospital stays. Adult and aged individuals lose muscle mass at similar rates during periods of disuse; however, only aged skeletal muscle fails to fully recover once activity resumes. Current efforts to facilitate skeletal muscle recovery are aimed at increasing myofibrillar protein synthesis by stimulating mTORC1(mammalian target of rapamycin complex 1), a major regulator of protein synthesis. However, we showed that skeletal muscle in aged rats already has higher rates of myofibrillar protein synthesis and mTORC1 activity than adult rats. We also showed that aged skeletal muscle has an accumulation of insoluble ubiquitinated proteins compared to adult muscle, indicating impaired proteostasis and possibly impaired autophagy degradation. We hypothesized that mTORC1 inhibition via rapamycin administration would reduce protein synthesis and the accumulation of p62 aggregates, facilitating recovery in aged skeletal muscle after disuse. Methods: Adult (10 months) and old (26 months) OKC HET rats were hindlimb unloaded (HU) for 14-days to induce atrophy, followed by subsequent 14 days of reloading (RE) through normal ambulation. Animals were fed either a control or rapamycin-supplemented (42 ppm) diet. To determine bulk protein synthesis, rats were labeled with deuterium oxide (D2O) during weight bearing (WB), HU, and RE, (n=4-6 per time point per group). Finally, to assess the presence of autophagy related protein aggregates we immuno stained for Sequestosome 1/p62, an autophagy cargo receptor protein. Results: Our data showed that myofibrillar protein synthesis rates were elevated in the old muscle compared to the adult ( k = 0.029 1/day ±0.002 vs. 0.039 1/day ±0.002, p<0.0001), and that protein synthesis rates were lower in the old rapamycin cohort (k = 1/day ±0.002 vs. 1/day ±0.003, p<0.0001). Furthermore, p62 puncta was three-fold more abundant (p<0.01) in aged skeletal muscle, compared to the adult muscle. Although the sample size is small, when comparing p62 puncta in the old rapamycin group to the old controls, there was no difference between the cohorts. Conclusion: We show that mTORC1 inhibition reduces protein synthesis in aged skeletal muscle. We also show that aged muscle has more p62 aggregates compared to adult skeletal muscle, indicating that autophagy related targets are not being degraded effciently with age. Further analyses will assess the effects of mTORC1 inhibition on other proteostatic mechanisms in atrophied skeletal muscle of aged rats.

NIA Training Grant: 5T32AG052363-04VA I01 BX005592 APS SURF.

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.
Characterization of Sex-Dependent Differences in Brain Microvascular Bioenergetics
Authors: Sure Venkata , sakamuri Siva , Oruganti Lokanatha , Chandra Partha , merdzo Ivan , Lindsey Sarah , Mostany Ricardo
Published: May 2024

Background: Women experience increased incidence of stroke-related deaths and lifetime risk of Alzheimer's disease (AD). Microvascular dysfunction has been implicated in the pathogenesis of ischemic stroke and AD. Our objective is to investigate the sex-dependent differences in bioenergetics of young mouse brain microvessels (BMVs). Methods: BMVs were isolated from young male and female mice (3-4 months), using a combination of gradient centrifugation and filtration (300μm and 40μm filters) methods. Extracellular acidification rate (ECAR) and oxygen consumption rate (OCR) of BMVs were measured utilizing the Agilent Seahorse XFe 24 analyzer. The levels of proteins and mRNAs of mitochondrial respiratory complexes were measured by western blot and RT-PCR, respectively. Citrate synthase (CS) enzyme activity and ATP levels were determined in lysates of BMVs. Results: Real-Time ATP Rate assay demonstrated a decreased total ATP production rate and ATP contribution from both glycolysis and oxidative phosphorylation (OxPhos) in BMVs from females compared to males. Mitochondrial stress test assay revealed significantly lower values of several mitochondrial respiratory parameters, including basal respiration, ATP production, maximal respiration, spare respiratory capacity, and proton leak in BMVs from females compared to males. Glycolytic Rate assay uncovered reduced basal glycolysis, proton efflux rate (PER) originating from basal glycolysis, and the mitoOCR/glycoPER ratio in BMVs from females compared to males. Interestingly, no sex-dependent differences were observed in basal PER and post-2-DG acidification rates in BMVs. Mito Fuel Flex Test assay showed no sex-dependent difference in the utilization of glucose, glutamine, and long-chain fatty acids as fuel substrates in BMVs. ATP measurements confirmed the reduced ATP levels in BMVs from females compared to males. Measurements of CS activity revealed no sex-dependent difference in the BMVs. Lastly, Western blot and RT-PCR experiments indicated no differences in either protein or mRNA levels of various mitochondrial complex protein levels.Conclusions: Female BMVs showed reduced mitochondrial respiratory and glycolytic parameters compared to male BMVs although relative contribution of various substrates for energy production were not different. These sex-dependent differences involving glycolysis and OxPhos make the microvasculature vulnerable to injury in females.

Funding sources: NIH grants AG074489 and NS114286 (PVGK and RM).

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.
Functional profiling of resident cells during vascular aging
Authors: Brady Travis , Gerecht Sharon , Santhanam Lakshmi
Published: May 2024

Introduction: Depending on surrounding cell types, substrate mechanics, and chemical agonists, vascular cell types – including endothelial (ECs) and smooth muscle cells (VSMC) — modulate their behavior to maintain homeostasis. Aging perturbs this homeostasis resulting in EC and SMC dysfunction, marked by impaired barrier integrity and pathological ECM remodeling. Endothelial-to-mesenchymal transition (EndMT) in ECs and “dedifferentiation” of VSMCs towards a synthetic phenotype are phenomenon under investigation as cellular drivers of the widespread dysregulation seen with aging. The overall goal of this project is to understand the effect of cross-talk between ECM and growth factor signaling on vascular cell plasticity during aging. Materials and Methods: Human aortic endothelial cells (HAECs) were seeded onto transwell inserts after seven days treatment with or without TGF-β. After growing to confluence on the insert, cells were subjected to a FITC-dextran transwell assay. A parallel group of cells was seeded onto fibronectin coated glass-bottom dishes and stained for the expression of focal adhesion proteins and cell-type markers. Mouse aortic smooth muscle cells (maSMCs) were isolated from C57Bl6 mice at 3 (young), 6 (early middle-aged; EMA), 9 (middle-age; MA), or greater than 18 months of age (old). Cells were seeded onto dye-quenched (DQ) collagen type I (Col-I) substrate before gain of fluorescence was measured in proximity to the cell as well as in the surrounding media. A parallel group of cells were allowed to grow in media containing FITC Col-I, and gain of fluorescence was measured in proximity to the cells. Each cell type (3M, 6M, 9M, and 18M) in both experiments (DQ and FITC) were further treated with MMP inhibitor, TG2 inhibitor and TGF-β1 to measure their impacts on Col-I turnover. Results: Barrier function was not impaired in ECs cultured with TGF-β1, relative to their untreated counterparts. Mouse aortic SMCs isolated from older mice had decreased rates of Col-I cleavage and were more susceptible to MMP inhibition than their younger counterparts. Conclusions: maSMCs from older mice have lower Col-I turnover than their younger counterparts. This is consistent with bulk tissue behavior, as it is well known that relative collagen levels increase in the elastic vasculature as we age. TGF-β1 treatment did not have an effect on permeability of 4kd FITC-dextran, it is feasible that there will be an impact on the larger 70kd fragments.

Travis Brady is supported by the NASEM Ford Foundation Pre-doctoral Fellowship.

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.
Antillean manatees (Trichechus manatus) tolerate acute food deprivation associated with a modest reduction in body mass
Authors: Ruiz Maria Isabel , Rivera-Pérez Carla I. , Fernández-Martínez Ricardo , Mignucci-Giannoni Antonio A. , Ortiz Rudy M.
Published: May 2024

Acute food deprivation induces metabolic shifts toward a greater reliance on lipid metabolism to sustain homeostasis in marine mammals. Lipid utilization depends on diet, metabolic rate, environmental conditions, and food availability. Antillean manatees ( Trichechus manatus) are aquatic herbivores with two-layered fat deposits that can reduce their metabolic rate by 23% when fasting. However, the contributions of lipid metabolism during fasting and refeeding in manatees remain poorly understood. Three juvenile Antillean manatees under human care were food deprived for 64 hours under close medical watch, then refed. Body mass (BM) was measured before and after acute food deprivation over the course of the four days of the study. Plasma samples were collected 16 hours post-prandial control, 40 and 64 hours after food deprivation, and 16 hours post-re-feeding. Prior to deprivation, mean BM was 107.3 ± 5.2 kg, and 100.1 ± 4.3 kg after deprivation. LDL increased after 40 hours of fasting and decreased at 64 hours, whereas HDL peaked at 60 hours post-fast and decreased during refeeding. TG and VLDL increased after refeeding; however, there were no significant changes between deprivation and refeeding in the lipid panel suggesting that 64 hours of acute food deprivation is well tolerated. These data provide an insight to the metabolic tolerance of the Antillean manatee that may experience acute periods of food deprivation as animals migrate across habitats and/or as they experience habitat loss or seasonal food scarcity.

I. Ruiz was supported by NIH NIGMS URISE grant T34 GM145511.

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.
Time-Restricted Feeding Mitigates Age-Related Cognitive Decline: Impacts on Neurovascular Coupling and Blood-Brain Barrier
Authors: Sanford Madison , Negri Sharon , Reyff Zeke , Ballard Cade , Nyul-Toth Adam , Gulej Rafal , Csiszar Anna
Published: May 2024

Vascular cognitive impairment (VCI) and age-related cognitive decline are mediated by alterations in microvascular function, cerebral blood flow (CBF), neurovascular coupling (NVC) responses and blood-brain barrier (BBB) permeability. The pathogenesis of VCI can be influenced by lifestyle factors like exercise, nutrition, and dietary habits. Time-restricted feeding (TRF) offers an accessible intervention that can be employed during aging. This study is aimed at investigating the cerebromicrovascular effects of TRF on NVC responses and BBB integrity in aged mice to explore potential novel interventions against the age-related loss of cognitive function. We hypothesized that TRF would improve NVC responses and BBB integrity during aging to prevent age-related cognitive decline. To test this hypothesis, 18-month-old C57BL/6 mice were placed on TRF regimen for 6 months, where they received ad libitum feeding for 6 hours each day. 6- and 24-month-old mice fed 24 hours/day ad libitum were used as controls. All three groups were subjected to cognitive tests including radial-arms water maze (RAWM). NVC was assessed by measuring CBF using last speckle contrast imaging while performing contralateral whisker stimulation, and BBB integrity was measured through extravasation of tracers in various sizes using intravital two-photon imaging. We found that aged mice had significant impairment in NVC responses. 6 months of TRF improved BBB integrity and rescued NVC responses, and significantly improved learning and spatial memory. This study emphasizes the importance of maintaining cerebromicrovascular integrity to promote healthy brain aging and cognitive health. The establishment of the mechanisms by which TRF exerts benefits during aging provides pertinent information to the future development of therapeutic strategies to prevent VCI.

Stephenson Cancer Center, National Institute of Aging R03 AG070479, American Heart Association.

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.
Sex Differences in Youth Elite Swimming Performance
Authors: Morgan Ashley M. , James Jessica J. , Hunter Sandra K. , Joyner Michael J. , Coleman Doriane , Senefeld Jonathon W.
Published: May 2024

Purpose: While it is well-known that elite males are faster than elite females in all Olympic-length swimming events, less is known about the age of the divergence in swimming performance between the sexes. Thus, this observational study compared swimming performance of elite male and female youths. Methods: We collected the all-time best 100 U.S. freestyle swimming performance times of boys and girls aged 5 to 18 years for six freestyle swimming events from 50m to 1500m. We compared data using univariate ANOVAs and Chi-squared tests. Results: Swimming performance improved with increasing age for both boys and girls (p<0.001) until a plateau— which began at a younger age for girls (15 years) than boys (17 years; sex × age; p<0.001). Before age 8, there was no sex difference in swimming performance (p>0.05). Beginning at age 9 however, boys swimming performance was faster than girls (1.0% to 1.3% depending on distance), and this sex difference in performance increased in magnitude until 18 years (p<0.001; 6.6% to 11.0% depending on distance). While boys represent 50% of the top 100 age-group performances at ages 5 and 6, boys represent an increasingly larger proportion of top performances across years of age including nearly 100% of all top 100 age-group performances beginning at age 15—except for one notable female swimmer in the 1500m Conclusion: Among elite youth swimmers, boys have increasingly faster performances than girls beginning at age 9 years, with minimal sex differences in swimming performance before 9 years. Additionally, boys represent an increasingly larger proportion of the top 100 age-group performances of all-time.

No funding.

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 trepidatious return to in-person instruction during the COVID-19 pandemic: valuable lessons applied from online teaching using Lt in the face-to-face classroom
Authors: Ford Bridget
Published: May 2024

The speed at which educators have embraced new technologies during the COVID-19 pandemic has been remarkable. This pivot to virtual instruction has been particularly diffcult in courses where hands-on experiences are the norm, such as in anatomy and physiology laboratory courses. Now with the transition back to mostly in-person instruction, the anatomy and physiology lab environment has faced a new set of challenges where the want to return to a strictly hands-on experience is being met with the need to still maintain flexibility and accessibility for students placed in quarantine. The anatomy and physiology lab curriculum at the University of the Incarnate Word (UIW) has adapted to this varied set of needs by adopting the use of the web-based laboratory software platform, Lt. Students in introductory anatomy and physiology labs surveyed during strictly virtual semesters reported a high level of satisfaction with the Lt lab software. Ratings regarding ease of use, support of learning, and overall ratings increased each semester with the highest ratings occurring during the recent semesters where instruction returned to mostly in-person and hands-on (Fall 2021 – Spring 2022). Interestingly, beginning in 2022 and continuing into fall of 2023, ratings of overall satisfaction began to decrease. Although it is currently diffcult to determine the root cause of this decrease in satisfaction, we speculate that many students are becoming fatigued with the continued use of seemingly virtual labs. Although most lab exercises are hands-on and include dissections and live physiological recordings, we think that the continued use of a virtual interface is too reminiscent of learning under quarantine conditions. Even with variations in ratings regarding Lt use in our introductory anatomy and physiology laboratories, our data still help to support the widely held belief that students perform best, and that instruction is more effective with face-to-face laboratory courses. With our continued use of Lt, we have found an effective combination of virtual and in-person instruction that best fits our course outcomes while still supporting the flexibility and accessibility our students require.

Research reported in this poster was supported by the University of the Incarnate Word Offce of Research and Graduate Studies.

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.
Anabolic Signaling After Withdrawl of AMPK-Activating Drugs in C2C12 Cells
Authors: Dray Steven D. , Summers Abigail E. , DePierro Ethan A. , Johnson Kade G. , Thomson David M.
Published: May 2024

Adenosine monophosphate-activated protein kinase (AMPK) is a master metabolic regulator that is activated under low-energy conditions, which generally promotes catabolic processes, including an increase of ATP synthesis and inhibiting anabolic processes that consume ATP. Indeed, acute AMPK activation potently inhibits anabolic pathways, including Akt/mTORC1 signaling. However, recent research reported that withdrawal of the AMPK-activating drug AICAR after a short treatment period results in enhanced anabolic signaling through Akt/mTORC1. This work aims to extend those findings using a more specific AMPK activator since AICAR is well-known to have numerous AMPK-independent effects. To do so, we treated differentiated C2C12 cells with either 2 mM AICAR, 5uM MK8722 (a pan-AMPK activator), or vehicle control (DMSO) for 60 minutes. After 60 minutes of incubation with the drugs, the treatment media was removed, the cells were rinsed and lysed immediately or incubated with media without drug treatment for 30, 60, 120, or 180 minutes, and then lysed. Phosphorylation of ACC (as an indicator of AMPK activity) and anabolic markers Akt, p70 ribosomal protein S6 kinase (S6k), and eIF4E-binding protein (4EBP1) were measured by western blotting. ACC phosphorylation (reflective of AMPK activity) remained elevated through 180 minutes after drug withdrawal for both AICAR and MK8722. Both AKT and S6k phosphorylation remained suppressed for at least 60 minutes after withdrawal of both AICAR and MK8722 and were not elevated at any time point up to 3 hours after withdrawal of the drugs. In contrast to previously reported data, we conclude that anabolic signaling remains inhibited in skeletal muscle myotubes for up to 3 hours after 1 hour of pharmacological activation of AMPK.

This work was funded by a BYU Gerontology Grant.

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.
Sex Differences in Exercise-Induced Modulation of the Humoral Immune Response to Influenza Vaccination
Authors: Fink Ashley , Bock Hannah , Colleran Jack , Hinson Destin , Campos Manuel
Published: May 2024

Physical activity is known to modulate immune cell function and understanding its role in vaccine-induced immunity is critical for both optimizing vaccine strategies and implementing lifestyle factors that contribute to better immune health. This study aimed to elucidate the impact of physical activity on antibody responses following influenza vaccination, with a specific focus on biological sex differences among male and female cross-country athletes. Based on previous studies, we hypothesized that physical activity would increase immune responses, regardless of biological sex. Two cohorts of male and female Division III college cross-country runners and two cohorts of non-athletes (no physical activity) participated in this longitudinal investigation. Studies were conducted in two separate influenza seasons where participants received a quadrivalent seasonal influenza vaccine (2020-21 and 2022-23). An estimated non-adjusted VO2 max was calculated, and a survey was administered to identify overall health status prior to the start of the study. Blood samples were collected at predefined intervals to assess pre- and post-vaccination antibody responses specific for the H1N1 component of each seasonal influenza vaccine. VO2 max, a measure of overall fitness, was higher in the athletes as compared to those participants who were not physically active, and these results were consistent among both males and females. All participants mounted an immune response to the seasonal influenza vaccine as indicated by a rise in vaccine-specific antibody titers from pre-vaccination to post-vaccination. However, the differences in titers were sex specific, with greater neutralizing antibody titers in females as compared to males — regardless of their level of physical activity. When data were further partitioned by physical activity level, it was identified that although males have lower antibody responses than females, males that were cross country runners had significantly greater antibody responses than males that were not physically active. This study contributes valuable insights into the complex interplay between exercise, sex, and immune responses. Understanding these dynamics could inform recommendations for individuals to be engaged in regular physical activity to optimize overall immune health.

This research was funded by a College of Saint Benedict and Saint John's University Faculty Development and Research Committee Award.

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.
Targeted Metabolic Profiling of Plasma in Lean and Obese Individuals during Oral Glucose Ingestion
Authors: Consitt Leslie , Saxena Gunjan , Law Timothy , Simon Janet , Maschari Dominic
Published: May 2024

Obesity has long been associated with metabolic inflexibility and insulin resistance. The purpose of this study was to determine 1) if the plasma metabolite/lipid profile was altered during an oral glucose tolerance test (OGTT) with obesity and 2) whether changes in plasma metabolites/lipids were related to insulin sensitivity or metabolic flexibility. Fourteen (7M/7F), young, lean (BMI: 21.9 ± 1.8 kg/m2) and fourteen (7M/7F) young, obese (BMI: 40.6 ± 5.4 kg/m2) individuals underwent a 2-hour OGTT with plasma samples obtained at baseline, 45 min and 120 min. Plasma was immediately stored at -80°C for subsequent targeted metabolomics (Biocrates MxP® Quant 500, Biocrates Life Sciences AG, Innsbruck, Austria). A 2 (body composition group) x 3 (time point) ANOVA was performed for each sex, with the false discovery rate (FDR q-value <0.10) used to account for multiple testing. Of the 73 small molecule metabolites tested, 2 (Glucose and Glutamate) differed between lean and obese females, and 34 metabolites (including 10 amino acids, 9 amino acid related, 5 bile acids, 2 biogenic amines and 2 carboxylic acids) changed with time in females. Of the 427 plasma lipid species tested, 79 (primarily triglycerides, TG) differed between lean and obese females, and 134 (primarily fatty acids and TG) changed with time. In males, 45 metabolites (similar to females) and 5 lipid species (Fatty acids only) changed with time. When examining the change in all plasma metabolites/lipid species from baseline to 120 min, the change in 9 TGs, 1 dihexosylceramide, as well as glycolithocholic acid sulfate (bile acid) were related to insulin sensitivity (Matsuda Index). Metabolic flexibility (change in respiratory exchange ratio from baseline to 120 min) was related to the change in 4 lysophosphatidylcholines, 3 TG, 2 acylcarnitines, 2 diglycerides, 3-Indoleacetic acid and glutamate.

American Heart Association Grant: 18AIREA33960404.

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.