bluuebunny/crossref_metadata_2025 huggingface dataset:
LncRNA H19 Regulates Intestinal Serotonin Transporter (SERT) Expression
Authors: Natarajan Anbazhagan Arivarasu , Frank Griggs Theodor , Sharma Dhara , Kaur Prabhdeep , Priyamavada Shubha , Jayawardena Dulari , Kumar Anoop , Saksena Seema , Alrefai Waddah , Tan Xiao-Di , Dudeja Pradeep , Gill Ravinder
Published: May 2023

Background: Serotonin transporter (SLC6A4; SERT) plays a key role in regulating the availability of 5-HT (5-hydroxytryptamine, a neurotransmitter and hormone) in the brain and the gut mucosa. A decrease in intestinal SERT expression, associated with increased availability of 5-HT, is implicated in the pathogenesis of infectious and inflammatory disorders of the gut. Therefore, it is critical to understand the regulation of SERT, as a novel target for the treatment of gastrointestinal disorders. In this regard, long noncoding RNAs (LncRNAs, small transcripts >200 nucleotides) are known to modulate gene expression via chromatin remodeling, transcriptional and posttranscriptional mechanisms. Notably, elevated levels of LncRNA H19 are observed in IBD patients and mouse models of inflammation and are known to promote mucosal regeneration and wound healing and restore the intestinal homeostasis. Whether LncRNA H19 regulates SERT expression remains unknown and was the focus of the current study. Methods: Caco-2 cells were transiently transfected with either H19 mammalian expression vector or H19 siRNA using Lipofectamine 2000. Protein and mRNA expression was measured by immunoblotting and real-time PCR, respectively. Age-matched H19 lncRNA- deficient mice and wild-type (WT) littermates were used to determine the role of genetic deletion of H19 on SERT expression in ileum. Results: H19 overexpression in Caco-2 cells increased SERT mRNA levels (~13-fold; p<0.05) at 48h post-transfection compared to an empty vector. Consistent with the mRNA levels, H19 also increased SERT protein expression (~2-fold, p<0.05). Furthermore, siRNA-mediated knockdown of H19 in Caco-2 cells resulted in a significant decrease in SERT mRNA levels (~80%, p<0.05). Parallel to the in vitro results, H19 deficient mice also showed a significant decrease in SERT mRNA expression (~69 %, p<0.05) in the ileum compared to the WT mice. Interestingly, in comparison to WT, the expression of other key transporters involved in intestinal NaCl absorption (SLC9A3, SLC26A3, and SLC26A6) remained unaltered in H19 deficient mice. Conclusion: These data demonstrate a novel role of LncRNA H19 in regulating the expression of SERT in the intestine under physiological conditions. We speculate that H19 mediated increase in SERT expression may provide valuable insights into the mechanisms restoring decreased SERT expression in inflammatory or infectious diseases of the gut. (Supported by VA/NIH).

VA and NIH

This is the full abstract presented at the American Physiology Summit 2023 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 microvascular outcomes with ischemic pre-conditioning and passive stretch
Authors: Fenn Sarah , Walker Maxwell , Bekkedal Lukas , Bundy Rob , Bratsch Amanda , Caldwell Jacob
Published: May 2023

INTRODUCTION: Passive stretching (PS) elicits hypoxia of the skeletal muscle that is similar to limb occlusion like that shown with ischemic pre-conditioning (IPC). However, the magnitude of responses between PS and IPC as they pertain to vascular outcomes are unknown. The purpose of this study is to investigate intermittent passive stretch to intermittent ischemic pre-conditioning on microvascular responsiveness. Given the increased metabolic activity during PS, we hypothesized that passive stretch will be a more effective method to improve microvascular function than IPC. METHODS: 5 preliminary college-aged subjects participated in this randomized, crossover, study that included 2 lab visits with a one-week washout period. Each visit started with a rest period where baseline blood pressure and heart rate were taken. A post occlusive reactive hyperemia (PORH) test was performed prior to and after each intervention. An intervention of PS or IPC consisting of 5-minutes “on” 5-minutes “off” four times through occurred after pre-testing. IPC consisted of bilateral cuff inflation on the upper thigh to 220mmHG to ensure full occlusion. PS consisted of splinting devices placed bilaterally on the subject’s feet where they were stretched to a degree of moderate discomfort. The PORH was repeated after each intervention. A 2-way repeated measures ANOVA was performed to compare group (PS vs. IPC) by time (pre vs. post). Statistical significance was set at p<0.05. RESULTS: Our preliminary data suggest a main effect of time for IPC (p=0.04) (pre: 0.071 ± 0.029 %/s-1), (post 0.095 ± 0.028 %/s-1) and posed a tendency (p=0.11) for PS (pre: 0.064 ± 0.040 %/s-1), (post: 0.080 ± 0.030 %/s-1) to increase microvascular responsiveness. In either group, slope 1; resting muscle metabolism was not significantly different (p>0.05). CONCLUSION: The current preliminary results suggest that PS, a foreseeable asset to macrovascular modulation, may also present itself as an impactful facilitator for microvascular responsiveness when compared to IPC. However, more data is needed to further solidify this relationship.

This study was funded through supported start-up funds by the University of Wisconsin-La Crosse.

This is the full abstract presented at the American Physiology Summit 2023 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.
Aerobic exercise training attenuates the peak blood pressure response to exercise in chronic kidney disease
Authors: Mehrer Justin , Stock Joesph , Kirkman Danielle , Edwards David
Published: May 2023

Chronic kidney disease (CKD) is an expanding public health problem. Patients with CKD have reduced exercise tolerance and are at a high risk for cardiovascular disease and events. Previous work has demonstrated that an exaggerated blood pressure response to exercise occurs in these patients which may contribute to their poor exercise capacity and increased cardiovascular risk. The purpose of this study was to test the hypothesis that 12 weeks of aerobic exercise training would attenuate the peak blood pressure response to exercise in patients with CKD. METHODS: Twenty-eight patients with stage 3 and 4 CKD (mean±SD: estimated glomerular filtration rate 43 ± 12 ml/min/1.73 m2) were randomly allocated to an exercise training (EX) or control (CON) group. EX consisted of 12 weeks of supervised aerobic exercise 3 times per week. Exercise duration and intensity progressively increased to 45 minutes at 65% to 85% heart rate reserve. CON received routine care. Cardiopulmonary exercise testing was performed on a cycle ergometer at baseline and following 12 weeks. Exercise intensity increased by 15W every minute and automated breath-by-breath gas analysis averaged over 10 seconds intervals was acquired throughout the protocol. Blood pressure (Tango M2, SunTech, NC) was recorded at rest and every 2 min throughout exercise and recovery. RESULTS: Twelve weeks of EX increased both VO2peak (p<0.01) and exercise duration (p<0.01). At 12 weeks, peak systolic blood pressure was not different from baseline in the EX (207 ± 32 vs 206 ± 35 mmHg; p=0.86) or CON groups (192 ± 39 vs 194 ± 39 mmHg; p=0.85). Exercise training significantly reduced peak diastolic blood pressure (91 ± 14 vs 81 ± 14; p = 0.002) whereas this was unchanged in the CON group (82 ± 15 vs 84 ± 15 mmHg; p=0.66). CONCLUSION: Twelve weeks of aerobic exercise training improved exercise capacity and attenuated peak diastolic blood pressure during exercise in patients with stage 3 & 4 CKD. The reduced blood pressure reactivity observed following exercise training in CKD may reduce cardiovascular risk and requires further investigation.

Funding source: National Institutes of Health, National Heart Lung and Blood Institute grant R01HL113514

This is the full abstract presented at the American Physiology Summit 2023 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.
Early Spinal Microglial and Non-microglial Cell Responses to Systemic LPS in Rats
Authors: Nikodemova Maria , Berschel Mackenzie , Michaelson Alysha , Parikh Komal , Mitchell Gordon
Published: May 2023

Systemic inflammation associated with a wide range of clinical disorders elicits neuroinflammation in the CNS, exacerbating neurodegeneration or traumatic/ischemic injuries. Neuroinflammation also impairs important forms of neuroplasticity associated with cognitive and motor learning. Several mechanisms propagate systemic inflammation into the CNS, although important details are not yet understood. Reports suggest propagation via vagal pro—inflammatory sensory afferent neurons, and/or cytokines crossing the blood-brain barrier. Microglia are the resident CNS immune cells, and are key contributors to CNS neuroinflammation, producing cytokines, chemokines, NO and ROS. Important contributions are also known from other CNS cells ( e.g. astrocytes, pericytes and neurons). Here, we investigated CNS responses to systemic inflammation induced by systemic LPS injection (1mg/kg, i.p.) in 3 months old Sprague-Dawley rats to test an early stage in the neuroinflammatory process. Three hours post-LPS injection, rats were perfused with PBS followed by microglia isolation from cortex and cervical spinal cord via immunomagnetic separation; the microglia-free fraction (neurons, astrocytes, pericytes, and other cells) was also collected for analysis. The efficacy of microglial isolation was verified by flow cytometry, and both microglial and non-microglial mRNAs were analyzed via qRT-PCR. CD200 and CX3CL1 (fractalkine) are two proteins expressed exclusively by neurons that mediate neuron-microglial communication by interacting with microglial receptors. Post-LPS, both CD200 and CX3CL1 increased 2.5 and 8 fold, respectively. Colony stimulating factor 1 (CSF-1), a protein produced by astrocytes and oligodendrocytes that is crucial for microglial survival, increased 5-fold. Surprisingly, inflammatory cytokines IL6, IL1β, CCL2, iNOS and TNFα were significantly elevated in non-microglial cells, but only IL6 and iNOS were increased in microglia 3 hours post-LPS. Thus, non-microglial cell responses to systemic inflammation appear to occur prior to full microglial activation. We hypothesize that peripheral pro-inflammatory signals propagate into CNS via pericytes and/or astrocytes that are in close contact with blood vessels. Further studies are needed to identify specific cellular sources of pro-inflammatory cytokines. Since CD200 prevents excessive inflammation in peripheral tissues, we also hypothesize that neuronal CD200 upregulation limits microglial immune responses, preventing inappropriate over-activation.

Supported by: R01 HL149800 & HL147554

This is the full abstract presented at the American Physiology Summit 2023 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 the erythropoietin response to hot tub treatment and carbon monoxide inhalation
Authors: DiMarco Kaitlyn , Chapman Christopher , Matsell Emma , Weiser Natasha , Grivette Margaret , Lucernoni Katie , Halliwill John , Lovering Andrew , Minson Christopher
Published: May 2023

The kidney increases erythropoietin (EPO) when oxygen delivery is reduced, and when reductions in oxygen delivery are sustained, increased EPO results in increased red blood cell (RBC) production. More recently, carbon monoxide (CO) and heat have been used chronically to increase RBC production and therefore hemoglobin (Hb) mass. However, studies examining the acute effects of these interventions are limited, and no studies have examined these interventions in women. The purpose of this study was to examine the effects of CO inhalation and heat treatment alone and in combination on circulating EPO and determine if there are sex differences in these responses. 11 healthy subjects completed the study (6 women). Baseline blood was drawn to measure iron, ferritin, and transferrin concentrations. Hb mass was measured via the 10-minute CO-rebreathe method. Subjects completed three interventions – CO inhalation (carboxyhemoglobin 13.01±2.5%) hot tub immersion (40 degrees C for 45 minutes), and combined CO and hot tub – in a randomized crossover design. Renal blood velocity (RBV) was measured via ultrasound during all interventions. Venous blood was drawn at baseline and every hour for 6 hours post-intervention for measurements of EPO. All interventions reduced renal oxygen delivery (Δ47.5±21mL O2/min), and there were no sex differences in the reduction in oxygen delivery. All three treatments similarly increased EPO from baseline to peak concentration (Δ4.94±5.6mIU/mL). Women had a significantly greater increase in EPO than men to all three interventions (Δwomen 8.22±5.6mIU/mL; Δmen 1±2.06mIU/mL). The degree of EPO increase on all three days negatively correlated with Hb mass (R2=0.64) and positively correlated with transferrin (R2=0.73). Women may respond better to these interventions aimed to increase EPO, but the degree of responsiveness may depend on baseline Hb mass as well as transferrin concentrations.

Wu-Tsai Human Performance Alliance at Oregon

This is the full abstract presented at the American Physiology Summit 2023 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.
Skeletal muscle reactive hyperemia is dependent on the deoxygenation stimulus in young healthy humans
Authors: Durbin William , Kirby Brett , Crecelius Anne
Published: May 2023

Reactive hyperemia tests create mismatches in oxygen (O2) delivery and demand by occluding blood flow and O2 delivery in the face of stable quiescent skeletal muscle O2 demand. We tested the hypothesis that skeletal muscle reactive hyperemia is dependent on the specific deoxygenation stimulus. We hypothesized that the magnitude of deoxygenation (Δ=nadir-baseline) would correlate with the magnitude of the reactive hyperemic response (Δ=peak-baseline), whereas the total deoxygenation (O2 debt, calculated as the total area under the curve of deoxygenation, below baseline) would correlate with the total reactive hyperemic response (area under the reactive hyperemia curve, above baseline). In six (3M:3F) young healthy adults, we continuously measured forearm blood flow using doppler ultrasound on the brachial artery and muscle O2 saturation via near-infrared spectroscopy (MOXY) during three lengthening occlusion timed-reactive hyperemia tests (1, 5, or 10 minutes in duration). The magnitude of deoxygenation was significantly (P<0.05 via paired t-test) less during 1 min occlusion (-13±1.6%) compared to either 5 min occlusion (-67±14%; P=0.0015) or 10 min occlusion (-74±10%; P=0.0004), but 5 min vs 10 min occlusion were not different (P=0.40). Similarly, the magnitude of the RH was greater in both the 10 min occlusion (329±102 ml/min; P=0.0004) and 5 min occlusion (295±123 ml/min; P=0.005) vs 1 min occlusion (131±69 ml/min; P<0.0001), but were not different from one another (P=0.11). However, the total deoxygenation increased progressively from 1 min (-335±51 units), to 5 min (-10732±2209 units), to 10 min (-32357±5053 units; all P<0.01) as did the total reactive hyperemic response (1 min:1326±927 ml; 5 min:7865±4055 ml; 10 min:17447±9698 ml; P<0.01). These results suggest that two distinct deoxygenation factors, the absolute magnitude of and the total mismatch between O2 supply and demand, may guide human skeletal muscle's reactive hyperemic response profile. The increased duration in a deoxygenated state observed in the 10 min occlusion leads to a greater overall reactive hyperemia response, potentially mediated by increased muscle metabolite production and greater bioavailability of vasoactive products mediated by the fully deoxygenated erythrocytes.

This is the full abstract presented at the American Physiology Summit 2023 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.
No effect of nitric oxide on pulmonary pressure response to SCUBA diving
Authors: DiMarco Kaitlyn , Futral Eben , Drvis Ivan , Glavicic Igor , Lord Rachel , Banic Ivana , Dujic Zeljko , Lovering Andrew
Published: May 2023

Some SCUBA diving time and depth profiles have been shown to increase pulmonary artery systolic pressure (PASP) post-dive. SCUBA diving while breathing compressed air results in a hyperoxic fraction of inspired oxygen and SCUBA divers are not hypoxic following a dive, so hypoxic pulmonary vasoconstriction is not responsible for the observed increase in PASP. In addition, no studies to date have examined whether the increased PASP is due to vasoconstriction or increased cardiac output (Q) following the dive. The purpose of this study was to examine whether nitric oxide availability post-dive is associated with the increased pulmonary pressure following SCUBA diving. 26 subjects completed the study (6 female). Subjects completed two dives (18 meters of sea water, 47 minute bottom time) on back-to-back days. Subjects were given sildenafil or placebo in a randomized and balanced crossover design upon resurfacing from their dive. Cardiac ultrasound for measurements of PASP and Q were done before diving and 1 hour after drug ingestion upon resurfacing. Total pulmonary resistance (TPR) was calculated as PASP/Q. PASP (p=0.0186) and TPR (p=0.0156), but not Q (p=0.779), increased on day 1 in the sildenafil group only. Irrespective of drug treatment, PASP was significantly higher by 2.58 mmHg at pre-dive on day 2 compared to pre-dive day 1 (p = 0.031). The increase in pulmonary pressure with SCUBA is likely independent of nitric oxide bioavailability. In addition, pulmonary pressure may remain mildly elevated for up to 24 hours after a SCUBA dive at 18m for 47 minutes.

PADI Foundation Diving Physiology Grant (2021 - 2022), Title: Is SCUBA diving-induced pulmonary hypertension related to blood flow through patent foramen ovale and inflammation? AT Lovering (PI), Zeljko Dujic (Co-I); Fulbright Scholars Program (2019 & 2022), Title: Investigating the role of intrapulmonary and intracardiac shunts in mediating breath-hold diving-induced and SCUBA diving-induced pulmonary hypertension. A.T. Lovering (PI); University of Oregon College of Arts & Sciences International Research Travel Grant (2022), AT Lovering (PI); Global Oregon Faculty Research Travel program (2022), AT Lovering (PI)

This is the full abstract presented at the American Physiology Summit 2023 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.
Paradoxically reduced pulmonary vascular resistance and abnormal vascular remodeling in the obese spontaneously hypertensive heart failure ZSF1 rats
Authors: Buncha Vadym , Bagi Zsolt
Published: May 2023

Pulmonary arterial dysfunction and remodeling often develop secondary to left heart disease and systemic hypertension. Excessive body weight is a well-established independent risk factor for the development of cardiovascular disease. However, data have emerged that for heart failure associated pulmonary complications obesity displays a lower long-term mortality. The impact of obesity on hypertension-related heart failure in affecting pulmonary vascular changes is incompletely understood. Here, we examined pulmonary vascular resistance and pulmonary artery function and remodeling in obese diabetic Zucker fatty/spontaneously hypertensive heart failure F1 hybrid (ZSF1) rats. 20-week-old male obese ZSF1 rats display increased left ventricle (LV) hypertrophy and diastolic dysfunction, when compared to age-matched lean spontaneously hypertensive heart failure (SHHR). Pulmonary vascular resistance, pulmonary arterial function and vascular wall remodeling were examined in isolated and perfused, ventilated lung preparations and isolated small pulmonary artery pressure and wire myography, respectively. We found that the pulmonary vascular resistance (normalized to lung weight) was significantly reduced in obese ZSF1 rats compared to SHHR (ZSF1: 0.2±0.02 mmHg·mL-1·min·g-1 vs SHHR: 0.29±0.018 mmHg·mL-1·min·g-1, p=0.01). In isolated pulmonary arteries the acetylcholine-induced relaxation was maintained, whereas the nitric oxide donor, sodium nitroprusside-induced relaxation was reduced in obese ZSF1 rats (SNP -log(IC50) ZSF1: 4.185±0.166 vs SHHR: 4.96±0.136, p=0.005). The wall thickness and wall-to-lumen ratio of pulmonary arteries were higher in the obese ZSF1 rats when compared to SHHR. Collectively, we found that obesity is associated with a reduced pulmonary vascular resistance and abnormal pulmonary artery remodeling in rats with systemic hypertension and diastolic heart failure, which may have implications in the clinically observed obesity paradox.

This is the full abstract presented at the American Physiology Summit 2023 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.
Eardrum tuning of the túngara frog
Authors: Wong Robert , Gridi-Papp Marcos , Paduano Mary , Tang Justine , Lee Betty , Morozumi Mark , Vo Trisha
Published: May 2023

Frogs rely heavily on acoustic communication to mediate their social interactions in reproduction. The frequency tuning of their ears tends to match that of the calls promoting effective communication. In small species such as the túngara frog, extratympanic pathways involving the body wall and lungs can also be relevant routes of sound reception. Electrophysiological recordings from the midbrain of the túngara frog indicate the greatest auditory sensitivity around 1-1.1 kHz and elevated around 2 kHz. This tuning is a close match to the peaks in their calls (around 1000 Hz for whine and 2400 Hz for chuck) and reaches surprisingly low frequencies considering their small body size, raising the question of how is the low peak received by the auditory system. We characterized the tuning of the eardrums and body walls using Doppler laser vibrometry while stimulating anesthetized subjects with a series of pure tones ranging from 0.2 to 18 kHz and having an amplitude of 80 dB at the subject. Each data set was collected in 5 repetitions with the auditory stimulus and 5 repetitions without the auditory stimulus as a control. The eardrum was expected to be the main auditory pathway and the body wall was a secondary but relevant pathway potentially tunned to lower frequencies. Both the eardrum and the body wall showed significant vibration response to the stimuli with the highest sensitivity at 2-3 kHz. This matches the auditory tuning of other small frogs but it is mismatched with the electrophysiological peaks at low frequencies recorded in previous studies. Our results indicate that either there is a significant loss (~ 50 dB) of the mating call's energy in the tungara frog's auditory system or that the low frequencies (< 1.5 kHz) are received through an undescribed mechanism.

Indirectly funded by an SAAG Grant.

This is the full abstract presented at the American Physiology Summit 2023 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.
Differential regulation of RhoA by TAS2R signaling in airway smooth muscle relaxation
Authors: Conaway Stanley , Hernandez-Lara Miguel , Deshpande Deepak
Published: May 2023

RATIONALE: Airway smooth muscle (ASM) hypercontraction and hyperresponsiveness are hallmark features of bronchoconstrictive disorders, which affect over 300 million people worldwide. Furthermore, the current standard of care, β-(adrenergic) agonists, lose their effectiveness for over 50% of patients that use them. Previous work in our lab resulted in the discovery of the expression of type 2 taste receptors (TAS2Rs) in human ASM. Interestingly, TAS2R agonists were found to elicit relaxation in a phospholipase C beta (PLCβ)-dependent manner. Furthermore, recent phosphoproteomics data from our group suggest that RhoA, an important contractile-related effector of PLCβ, is differentially regulated by TAS2R and β-agonists. Therefore, the goal of this study was to validate these findings and elucidate differences in the effects of multiple GPCR pathways on RhoA activity and ASM relaxation. METHODS: We determined the level of RhoA activity in human ASM cells (hASM) using the Rhotekin protein construct, which contains a Rho-binding domain with a high affinity for active RhoA. Additionally, we utilized lentiviral particles containing a single chain fluorescence resonance energy transfer (FRET) biosensor construct (RhoA2G) with a Rho-binding domain specific for active RhoA. Healthy hASMs were transduced with lentivirus and RhoA activity was monitored using fluorescent confocal microscopy. Cells were treated with TAS2R (chloroquine or flufenamic acid) or β (isoproterenol) agonists alone or in conjunction with the Gq agonist histamine to study the effects of these relaxant ligands on histamine-mediated RhoA activation. RESULTS: Our RhoA pulldown data using the Rhotekin construct showed that isoproterenol partially ablated histamine-mediated RhoA activation compared to the complete ablation of the signal by chloroquine (300 μM). Additionally, we observed complete ablation of histamine-mediated RhoA2G activity by isoproterenol while chloroquine and flufenamic acid evoked a reduction of histamine-mediated activity to below the observed baseline. This further validates our phosphoproteomics findings which suggest that histamine-mediated phosphorylation of ARHGEF12, a highly expressed RhoA activator, is partially attenuated by isoproterenol but fully attenuated by chloroquine (300 μM). Further, the RhoA FRET biosensor was useful in assessing the activation kinetics of RhoA in hASMs in real time. CONCLUSION: RhoA is an important contractile-related effector that is regulated differentially by isoproterenol and TAS2R agonists to evoke ASM relaxation.

The studies in this abstract are funded by the NHLBI Diversity Supplement for the NIH grant R01-HL137030 (D.A. Deshpande)

This is the full abstract presented at the American Physiology Summit 2023 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 Three Bovine Plasma Protein Fractions on the Human Gut Microbiota
Authors: Okerlund Adam , Van den Abbeele Pieter , Detzel Christopher , Rose Alexis , Deyaert Stef , Baudot Aurélien , Warner Christopher
Published: May 2023

The gut microbiome plays a crucial role in the health of its host by regulating metabolism and protecting against pathogens. One of the key functions of the gut microbiome is to produce short-chain fatty acids (SCFAs), including acetate, propionate, and butyrate. Though each SCFA has distinct health benefits, all SCFAs have anti-inflammatory effects and decrease the pH of the colonic lumen which increases mineral absorption and inhibits the growth of pathogens. Previous studies show that various fractions of bovine plasma positively impact the gut health, though their effect on the microbiome and SCFA levels is unknown. The objective of our study is to examine the effect of different bovine plasma fractions (whole plasma, crude bovine serum albumin [BSA], and immunoglobulins [SBI]) on the SCFA composition of the gut microbiome. We hypothesize that the bovine plasma fractions will alter the microbiome with an increase of SCFA abundance, with each of the three fractions performing uniquely.SIFR technology (Cryptobiotix) was used to investigate the effects of the three plasma products on the fermentation of fecal microbiota samples provided by six donors. Each protein fraction was subjected to oral, gastric, and small intestinal digestion, simulated small intestinal absorption, and colonic fermentation. Samples were analyzed by examining metabolic activity metrics, including the pH, gas levels, abundance of various SCFAs and branched-chain fatty acids (BCFAs), and microbial composition by quantitative 16S rRNA gene profiling. The addition of any of the three bovine plasma fractions (5 g) showed significant changes in microbial activity, including the increase in acetate, propionate, and butyrate (p < 0.001), with the addition of SBI having the largest effect, followed by whole plasma then BSA. The increase in the SCFAs was accompanied by an increase of bacteria known to produce SCFAs for all dosed protein fractions, with the SBI fraction giving significant increases in Firmicutes (p < 0.05) and Bacteroides (p < 0.01) compared to the blank. Overall, the addition of bovine plasma fractions into an in vitro gut model increases SCFAs, including acetate, propionate, and butyrate, with SBI showing the largest impact. Though SBI is known to bind and neutralize opportunistic pathogens by immune and steric exclusion mechanisms in the gut, this work suggests that SBI further promotes gut health by increasing SCFAs and the bacteria that produce them.

Commercial - Proliant Health and Biologicals funded the research.

This is the full abstract presented at the American Physiology Summit 2023 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.
PCAF regulates cardiac muscle function via non-epigenetic regulation of ACTA1 acetylation
Authors: Habibian Justine , Evans Levi , Ferguson Bradley
Published: May 2023

Historically, lysine acetylation has been studied in the epigenetic regulation of gene expression, in which it is known to play key roles in cardiac remodeling and dysfunction. However, recent evidence suggests that non-histone protein acetylation of myofilament proteins is also important for the regulation of cardiac contractility and relaxation. Lysine acetyltransferase (KAT) enzymes serve as writer proteins to acetylate histone and non-histone proteins. PCAF (p300/CBP associated factor) belongs to the GNAT family of lysine acetyltransferases and has been implicated in left ventricular hypertrophy (LVH), in which pharmacological inhibition of PCAF attenuated stress-induced LVH that was linked to changes in gene expression. Consistent with these reports, we show that garcinol, a p300/PCAF inhibitor, attenuated 2-weeks of isoproterenol-induced LVH, cardiac output (CO) and stroke volume (SV) in C57BL6J mice. Of interest, isoproterenol increased skeletal muscle alpha actin (ACTA1) protein acetylation in the left ventricle (LV) of mice and this was attenuated by garcinol treatment. ACTA1 is a fetal gene that is re-expressed in the myocardium of diseased hearts. These data imply that KATs acetylate (i.e. post-translational modification) this re-expressed gene, yet how acetylation of ACTA1 impacts cardiac function remains unclear. To determine this, we performed tail-vein injections of an adeno-associated virus (AAV) expressing either LacZ or an ACTA1 acetyl-mimic and performed echocardiography and gross morphology measurements in C57BL6J mice two-weeks post injection. Here, we report that pseudo-acetylation of ACTA1 increased LVH, and reduced fractional shortening (FS) and ejection fraction (EF) in mice. Lastly, we show that PCAF acetylated ACTA1 but not cardiac myosin; p300 failed to acetylate ACTA1 in vitro. Combined, these data suggest that PCAF acetylates ACTA1 to regulate cardiac contractility in response to β-adrenergic over-activation. While PCAF can serve as an epigenetic regulator of gene expression, these data highlight a non-epigenetic role for PCAF in cardiac function.

Funding: This research was funded by the USDA NIFA (Hatch-NEV00767), the Dennis Meiss & Janet Ralston Fund for Nutri-epigenetic Research, the National Institute for General Medical Sciences (NIGMS) of the NIH (P20 GM130459), the National Heart, Lung, and Blood Institute of the NIH (R15 HL143496), National Institute of Aging of the NIH (R21 AG077248) and NSF EPSCOR Track II (OIA-1826801) to B.S.F.

This is the full abstract presented at the American Physiology Summit 2023 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.
Dependence of cardiomyocyte force, velocity, and power generation on ATP concentration
Authors: Beard Daniel , Baker Anthony , Jezek Filip
Published: May 2023

Theoretical analysis and computer modeling of myocardial energy metabolism under physiological and heart failure conditions predicts that cytoplasmic ATP and ADP levels both fall roughly in proportion to reductions in total adenine nucleotide pool observed in heart failure. Assessing sub-maximal force and velocity in loaded myocardial muscle at MgATP levels in the range of 2 to 8 mM, Beard et al. ( Biophys. J. 2022. 121: 3213–3223) observed effects of MgATP on myocardial power generation that suggest that although maximal force and velocity are not substantially sensitive to differences in [MgATP] that occur in the normal versus failing myocardium, maximal power generation, which occurs at submaximal force and velocity, is sensitive to [MgATP]. Previously developed computational models are not able to reproduce the observed dependence on MgATP. The goals of the present study are to construct and analyze a computational model of muscle dynamics to analyze data on the dependence of maximal force, velocity, and power generation on [MgATP] in order to determine a potential mechanism to explain the MgATP-dependent phenomena. Model development and identification was guided by dynamic measurements on permeabilized mouse trabecular fibers. The data include force-velocity relation and time constant of tension development. The mathematical model used to simulate cardiomyocyte crossbridge mechanics was based on the previous crossbridge and calcium models from Tewari et al. (J Mol Cell Cardiol, 2016. 96: 11-25) and Campbell et al. (Biophys J, 2018. 115: 543-553). The developed model includes strain- and metabolite-dependent transition between attachment states, and ATP-dependent destabilization of the super-relaxed (SRX) myosin state. Model-based analysis of force and velocity dyanmics is consistent with the hypothesis that ATP assocition with the myosin protein influence the kinetics and thermodynamics of transitions between the SRX and disorded (DRX) states.

Funding: Department of Veterans Affairs Merit Review Award I01BX000740 (A.J.B.) and National Heart, Lung, and Blood Institute grant R01 HL154624 (A.J.B., D.A.B.)

This is the full abstract presented at the American Physiology Summit 2023 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.
Hydration status mediates racial differences in circulating copeptin among young adults
Authors: Linder Braxton , Hutchison Zach , Barnett Alex , Tharpe McKenna , Culver Meral , Jeong Soolim , Nichols Olivia , Watso Joseph , Fuller-Rowell Thomas , Robinson Austin
Published: May 2023

Background: Arginine vasopressin production is directly associated with increased cardiometabolic disease risk. Hydration influences the release of arginine vasopressin which can be measured using the surrogate marker copeptin. Furthermore, there are well documented race differences in both hydration status and copeptin. However, it remains unclear whether race differences in hydration status contribute to racial differences in copeptin. Therefore, the purpose of this analysis was to determine whether hydration status mediates observed racial disparities in plasma copeptin concentration. Methods: 54 young adults (24 Black: 15 female/9 male, 21.6 ± 0.7 years; 30 White: 12 female/18 male, 21.3 ± 0.8 years) were included in this analysis. Participants were instructed to follow their normal food and fluid intake practices and collect a 24-hour urine sample. We assessed hydration status via urine osmolarity (OSM) and specific gravity (USG). We also assessed plasma copeptin concentration as a surrogate measure of arginine vasopressin. Independent sample T-tests (normally distributed data) and Mann-Whitney U tests (non-normally distributed data) were used for racial comparisons for descriptive data and hydration biomarkers. We used Cohen’s d as a measure of effect size. Mediation analysis was used to determine whether hydration status (OSM and USG) mediated potential racial differences in plasma copeptin concentration. Significance was set a priori as p ≤ 0.05. Results: Black adults exhibited higher urine OSM (Black 640 ± 534, White 439 ± 303; p = 0.007, d = 0.435), USG (Black 1.020 ± 0.001, White 1.015 ± 0.001; p = 0.043, d = 0.569), and plasma copeptin concentrations (Black 6.22 ± 3.1, White 4.62 ± 2.4; p = 0.046, d = 0.329). Regarding mediation, OSM mediated 66% of the racial difference in plasma copeptin concentrations (β = 1.022 [standard error: 0.46], p = 0.027) and USG mediated 47% of the racial difference in plasma copeptin concentrations (β = 0.745 [standard error: 0.40], p = 0.064). Conclusions: Young Black adults exhibited higher urine OSM, USG, and circulating copeptin than young White adults; and differences in USG, and particularly OSM, mediate the race difference in copeptin. Although additional data are needed, the significance of our findings are that racial differences in hydration status appear to be a major driver of racial disparities in arginine vasopressin, as opposed to an inherent physiological difference.

Auburn University Presidential Graduate Research Fellowship (BAL); UAB CCTS TL-1 Program (UL1TR003096) (BAL); NIH Grant K01 HL147998 (ATR)

This is the full abstract presented at the American Physiology Summit 2023 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 role of the Locus Coeruleus in context-dependent respiratory tolerance to opioids
Authors: Szujewski Caroline , Sullere Shivang , Warden Matthew , Garcia Alfredo
Published: May 2023

Pairing an environmental context with repeat opioid use (ROU) can result in increased tolerance to the effects of the opioid. This context-dependent tolerance has been extensively studied with respect to the analgesic effects of opioids, yet a knowledge gap exists in understanding whether there is context-dependent tolerance that develops in opioid induced respiratory depression (OIRD). While activity in the Locus Coeruleus (LC), the primary noradrenergic center of the brain, is involved in cue-reward related behaviors, it also enhances breathing in response to changes in blood gas homeostasis. The objective of this study is to investigate the role of the LC in context-dependent respiratory tolerance. Adult mice expressing GCaMP in the noradrenergic cells of the LC underwent a ROU protocol consisting of an initial five-day period of context pairing where each mouse was administered fentanyl (0.7mg·kg-1·day-1; i.p.) in a distinctive fentanyl-paired context (FP), and saline was administered in different distinctive saline-paired (SP) context. Following context pairing, each mouse was administered fentanyl in both the FP and SP, while LC activity and breathing were simultaneously assessed using fiber photometry and unrestrained whole body plethysmography, respectively. Independent of context, fentanyl administration caused LC activity to increase and become rhythmic during OIRD (n=6). In the FP, however, the OIRD nadir occurred 10 min after fentanyl in all subjects (n=6/6); whereas the OIRD nadir in the SP occurred 5 min after fentanyl administration in the majority of subjects (n=5/6). The difference in time to OIRD nadir corresponded to a greater amount of LC activity in the FP prior to fentanyl (n=5 of 6, p=0.03) and during OIRD (n=5 of 6, p=0.021). These results implicate the potential involvement of LC activity and increased central noradrenergic status in producing context-dependent tolerance delaying the OIRD nadir. Our findings may be leveraged to better predict and/or mitigate overdose-related deaths associated with ROU.

NIH: R01NS107421; R01HL163965; R01DA057767

This is the full abstract presented at the American Physiology Summit 2023 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 Krtcap3 as a novel stress gene
Authors: Szalanczy Alexandria , Fitzpatrick Mackenzie , Bui Trangdai , Dyson Christina , Eller Seth , Giorgio Gina , Goff Emily , Landry Julia , Scott Christina , Seshie Osborne , Grzybowski Michael , Klotz Jason , Geurts Aron , Redei Eva , Weiner Jeff , Solberg Woods Leah
Published: May 2023

While obesity is an increasingly prevalent disease, genetic susceptibility is poorly understood and more research is sorely needed. Our lab has sought to confirm Keratinocyte-associated protein 3 ( Krtcap3) as a novel adiposity gene and characterize its role using an in vivo whole-body knock-out (KO) model on the Wistar-Kyoto (WKY) rat strain.We obtained conflicting adiposity and food intake results between two in vivo studies conducted before and after the COVID-19 pandemic, which brought along drastic environmental changes in the animal facility. Compared to pre-pandemic, in the quieter post-COVID-19 environment wild-type (WT) rats were eating more and gaining more weight, without corresponding changes in KO rats. We hypothesized that the prior environment had affected the stress levels of the rats, and that Krtcap3 may be a novel stress-related gene whose effects on adiposity are tangential.A significant environmental change was supported by altered expression of genes associated with glucocorticoid metabolism. Most interestingly, KO rats consistently have lower basal corticosterone (CORT) compared to WT rats and have a much stronger increase in CORT when their cage mate is removed for euthanasia.We have since sought to characterize the role Krtcap3 may play in the stress response. Despite the genotype differences in CORT response seen at euthanasia, there were no differences in the CORT response during a restraint test, indicating that both WT and KO are capable of responding to acute stressors. In WKY rats, there is high Krtcap3 expression in the pituitary gland and along the gastrointestinal tract, suggesting potential tissues of action for further investigation. Surprisingly, when we exposed WT and KO rats long-term to white noise and unpredictable mild stress, there was a stronger increase in the anxiety response of KO rats as compared to WT. This supports that Krtcap3 expression affects the response to stress, but suggests that the type of stress may also play a role. Taken together, these data demonstrate that Krtcap3 participates in the stress response. Though more work is needed to elucidate the finer mechanisms of the role of Krtcap3, these findings have important implications for human health, where stress is a known co-morbidity for many diseases, including obesity.

R01 DK106386, T32 DA041349

This is the full abstract presented at the American Physiology Summit 2023 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.
Oxygen-offloading rate from mouse Red Blood Cells of genetically diverse strains
Authors: Zhao Pan , Boron Walter
Published: May 2023

O2 diffusion across red blood cell (RBC) membranes is a critically important physiological process for the maintenance of life. Our previous work on murine RBCs ( bioRxiv. doi: 10.1101/2020.08.28.265066 ) showed that (a) the genetic deletion of aquaporin-1 (AQP1) and the Rh complex (mainly RhAG) together reduce O2 permeability of RBC membranes ( P M, O2) by ~55%, and (b) the double knockout (dKO) of AQP1 and RhAG plus pCMBS (sulfhydryl reagent and nonspecific inhibitor of membrane proteins that is nonetheless excluded from the RBC interior) reduces P M, O2 by ~91%. In order to identify the unknown membrane protein(s) that may function as O2 channels and contribute to the missing 91% – 55% = ~36% of P M, O2, we use comparative physiology. Using stopped-flow absorbance spectroscopy to monitor the hemoglobin (Hb) absorbance spectrum, we studied the oxygen-offloading rate from hemoglobin ( k HbO2) of RBCs from genetically diverse mouse strains. We compared two different mouse strains purchased from Jackson Labs—C57BL/6J and BALB/cJ with our standard mouse strain that ultimately derives from mice received from UCSF—C57BL/6Case. We found that, compared with C57BL/6Case, C57BL/6J mice have a k HbO2 for intact RBCs that is ~22% higher (N=18, 9 male plus 9 female, p<0.01), and a k HbO2 for pure hemolysate that is ~7% lower (N=12, 6 male plus 6 female, p<0.01). Comparing with C57BL/6Case, BALB/cJ mice have a k HbO2 for intact RBCs that is ~9% lower (N=18, 9 male plus 9 female, p<0.01), and a k HbO2 of pure hemolysate that is ~10% higher (N=12, 6 male plus 6 female, p<0.01). Because changes in k HbO2 of pure hemolysate are opposite in direction to changes in k HbO2 of intact RBCs, differences in Hb cannot contribute to the observed differences in O2-offloading rates in the two Jackson strains. Likewise, changes of mean corpuscular volume (MCV) and mean corpuscular hemoglobin concentration (MCHC), together, would only produce minor percent changes of k HbO2 in either C57BL/6J or BALB/cJ mice. Thus, it is likely that the differences in k HbO2 for intact RBCs among the three mouse strains reflect major differences in the O2 permeabilities of the RBC membranes. Planned comparative analyses of morphology (e.g., major diameter of biconcave discs), proteomics, lipidomics, and genomics (for deduced amino-acid sequences of proteins) will provide valuable insight into the contribution of specific membrane proteins and lipids to the relatively large differences in k HbO2 of intact RBCs between C57BL/6J and BALB/cJ mice.

Office of Naval Research (N00014-16-1-2535 and N00014-21-1-2366), and NIH research grant (1RO1HL 160857-01)

This is the full abstract presented at the American Physiology Summit 2023 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.