Peer Review Process Research Articles

In Appreciation of Our 2023 Reviewers and Volunteers

AbstractIn JGR‐Planets, the peer review process is critical to ensuring that the published articles are based on sound scientific principles, follow state‐of‐the‐art techniques while acknowledging relevant prior results, and present exciting discoveries or novel understanding of the fundamental processes that affect solar system objects. JGR‐Planets covers a broad range of topics addressing every aspect of geoscience with the only requirement that the work addresses planetary processes. The wide breadth of topics published is reflected by our editorial team composed in 2023 of associate editors Adrian Brown, Jun Cui, Joel Davis, Leigh Fletcher, Matthias Grott, Ananya Mallik, Germán Martínez, Molly McCanta, Katarina Miljkovic, Naomi Murdoch, Ryan Park, Arianna Piccialli, Andrew Poppe, Beatrix Sánchez‐Cano, Laura Schaefer, Mariek Schmidt, Yasuhito Sekine, Kelsi Singer, Michael Sori, Norihiko Sugimoto, Sonia Tikoo, David Trang, and Zhiyong Xiao in addition to the editors who authored this note. We rely on the expertise of the community to vet the articles submitted to the journal. In 2023, JGR‐Planets benefited from 1,184 reviews provided by 731 unique volunteer referees. We also received help from 19 guest editors working on four active special collections. To these volunteers: We are truly grateful that you chose to dedicate your time and energy to evaluate manuscripts and to advise us on the suitability of each manuscript for JGR‐Planets, often suggesting ways to improve the papers. We know that all our volunteers juggle many duties, both professional and personal. On behalf of the entire editorial board of JGR‐Planets, we express our heartfelt gratitude to the many scientists who support this journal. Thank you! You are performing a valued service to this journal and to the community.

Cystic fibrosis rescued using a reprogrammed porosome secretory machinery

Cystic fibrosis (CF) is a genetic disorder resulting in the secretion of highly viscous mucus in the airways, leading to lung infection, respiratory failure, morbidity and mortality. CF is attributed to mutation in the CF Transmembrane Conductance Regulator (CFTR) gene that codes for a chloride transporting channel at the cell plasma membrane. More than 2,000 mutations in the CF gene have been identified; however, the ΔF508 CFTR is the most common, accounting for approximately 70% of all CFTR mutations. Our earlier studies demonstrate the CFTR protein to be among the nearly 30 proteins constituting the porosome secretory machinery at the plasma membrane in human airway epithelial mucous-secreting cells. Our recent studies show that stimulated human airway epithelial cells pre-exposed to CFTR inhibitors result in loss of mucus secretion, suggesting the involvement of CFTR in porosome-mediated mucus secretion. To further test the hypothesis that CFTR is involved in porosome-mediated mucus secretion in the human airways, and to develop a therapeutic approach to overcome this defect in ΔF508 CFTR human bronchial epithelial cells, the current study was undertaken. Mass spectrometry and Western Blot analysis of porosomes isolated from WT-CFTR Human Bronchial Epithelial (HBE) Cells and ΔF508-CFTR CF HBE cells, demonstrate a varying loss or gain of several porosome proteins, including undetectable levels of the Ras GTPase activating like-protein IQGAP1 in the ΔF508-CFTR CF cells. This suggested that mutation in porosome-associated CFTR protein additionally affects other proteins within the porosome secretory machinery, negatively impacting mucus secretion. Therefore, to ameliorate defects in mucus secretion in CF, the reconstitution of functional porosomes obtained from WT-CFTR HBE cells into the plasma membrane of ΔF508-CFTR mutant cells was performed. Results from the study demonstrate that porosome reconstitution rescues mucus secretion approximately two- to four-fold more effectively than the currently available CF drugs including TRIKAFTA. Acknowledgements: Work presented in this article was supported by the Viron Molecular Medicine Institute and Porosome Therapeutics, Inc., Boston, MA. Competing Financial Interest: This work is patent protected by Porosome Therapeutics, Inc. The authors hold shares in the company. 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.

Effects of Heavy Alcohol Use on Fasting Glucose and Insulin Resistance in Mid-Life Adults

Introduction: As our population ages, type 2 diabetes has become more prevalent in the United States and one in five mid-life adults (50-64 years) have type 2 diabetes. Unhealthy and heavy alcohol use (that exceeds recommended drinking limits) causes dysfunction of the liver and pancreas that can impact glucose control and thereby increase risks of type 2 diabetes. In young adults, we previously found that fasting glucose and insulin resistance were not associated with heavy alcohol use. However, it remains unclear if heavy alcohol use contributes to the development of type 2 diabetes in an aged population. Therefore, the purpose of this study is to determine the effect of heavy alcohol use on fasting glucose and insulin resistance in apparently healthy mid-life adults. Methods: Mid-life men (n=21) and postmenopausal women (n=28), non-smokers, free of obesity and major clinical diseases, were recruited from the community around the Dallas—Fort Worth metroplex. All participants underwent physical exam and fasting blood sampling. Alcohol use was assessed by the US Alcohol Use Disorders Identification Test (USAUDIT) and a dried blood spot phosphatidylethanol (PEth) test. A PEth cutoff of 20 ng/mL was used to define heavy drinkers. Insulin resistance was assessed by calculating HOMA-IR (Homeostatic model assessment for insulin resistance) as insulin (μU/L) x glucose (nmol/L)/22.5. Results: A total of 24 participants had PEth levels of <20 ng/mL (non-heavy drinkers; PEth ranged from <limit of quantification to 13 ng/mL; mean ± SEM for age: 58±1 years and body mass index: 25.2±0.6 kg/m2) and the other 25 participants had PEth levels ≥20 ng/mL (heavy drinkers; PEth ranged from 20 to 665 ng/mL; age: 57±1 years and body mass index: 25.7±0.5 kg/m2). Heavy drinkers had higher USAUDIT scores than non-heavy drinkers (11.3±1.4 vs. 3.3±0.5, p<0.001). No significant difference between these two groups were found in lipid values (P≥0.1) as well as renal (P≥0.3) and liver function values (P≥0.08). Compared to non-heavy drinkers, heavy drinkers had a higher level of fasting blood glucose (96±2 vs. 91±1 mg/dL, P=0.02), but similar blood insulin (9.2±2.5 vs. 5.5±0.5 μIU/L, P=0.2) and HOMA-IR (2.23±0.64 vs. 1.23±0.11, P=0.1). The results for stepwise linear regression model indicate that only USAUDIT score was an independent factor of fasting glucose (B=0.59, p<0.001). Conclusion: Our results indicate that compared to mid-life adult non-heavy drinkers, heavy drinkers had higher fasting blood glucose levels, despite similar renal and liver function. Our results also indicate that higher risks of alcohol use disorder were associated with higher levels of fasting glucose. These data suggest that heavy alcohol use may have negative effects on glucose regulation in aged populations and increase risks of type 2 diabetes. This work was supported by NIAAA AA028537 to CLH. 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.

AAV-GAA Gene Therapy Clears Long Chain Length Neuronal Glycogen in a Pompe Disease Rat Model

Pompe disease is due to mutations in the acid a-glucosidase (GAA) gene. GAA protein degrades lysosomal glycogen and dysfunctional or absent protein leads to cellular glycogen accumulation. In recent years, it has become clear that glycogen accumulation in the central nervous system (CNS) needs to be targeted in Pompe disease. However, the standard of care — intravenous enzyme replacement therapy using recombinant GAA does not effectively target the CNS. Here, we investigated the ability of neonatal AAV-GAA therapy to clear neuronal glycogen in the Pompe ( Gaa−/−) rat. On post-natal day one, male Gaa−/− rats received an administration of AAV9-DES-hGAA (1x1014 vector genomes/kg) via the temporal vein injection or sham injection (1xPBS). Rats were euthanized at age 9 months, and spinal cords and the diaphragm muscle were harvested and glycogen biochemistry was evaluated by matrix-assisted laser desorption/ionization mass spectrometry glycogen imaging (MALDI) and immunohistochemistry (GAA antibody). MALDI imaging reveal significant reduction in glycogen accumulation in the cervical spinal cord, and AAV9-DES-hGAA selectively targeting longer glucose chains within glycogen. Immunohistochemistry verified GAA expression in spinal cord neurons of rats treated with AAV-GAA. In the diaphragm muscle, MALDI revealed that the expected increase glycogen in the untreated Pompe diaphragm was associated with a decrease in n-linked glycans, a potential biomarker of the disease. Strikingly, glycogen content and glycans in the AAV-GAA treated diaphragm were indistinguishable from wild type. We conclude the neonatal gene therapy with AAV9-DES-hGAA can drive functionally relevant GAA expression in the adult rat CNS, and also effectively targets the diaphragm. R01HD052682 (DDF and BJB), R01AG066653 (RCS), R01CA266004 (RCS), R01AG078702 (RCS), RM1NS133593 (RCS), R35NS116824 (MSG). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

A novel target for attenuating T1DM-induced myocardial ferroptosis

Background: The DMCM-AHEAD trial showed that lipotoxicity is a distinct feature of diabetic heart failure, which initiates and exacerbates cardiac pathogenesis in diabetic patients. Circulating iron levels are increased in diabetic patients. The combined presence of lipids and iron suggests a predominant role of ferroptosis in diabetes-induced heart failure. However, molecular targets for diabetes-induced myocardial ferroptosis remain unclear. In the T1DM heart, matrix metalloproteinase-9 (MMP9), a protease, is upregulated, and targeted deletion of MMP9 is cardioprotective. Hypothesis: Targeted deletion of MMP9 mitigates T1DM-induced myocardial ferroptosis. Methods and results: We performed in vitro studies on the loss and gain-of-function of MMP9 using human cardiomyocytes (AC16 cells). Overexpression of MMP9 downregulates (-1.55-fold p<0.001) GPX4, a key marker of ferroptosis, while inhibition of MMP9 upregulates (+2.03-fold p<0.001) GPX4 (n=6), suggesting a key role of MMP9 in GPX4 regulation and ferroptosis signaling. To determine the specific role of MMP9 in T1DM-induced ferroptosis, we evaluated ferroptosis markers in the heart (LV) tissue of male Insulin2 mutant (Ins2+/-) Akita (T1DM), littermate euglycemic Ins2+/+ WT, Akita/MMP9 knockout (MMP9KO), and MMP9KO mice (n=3-6). The cardiac levels of Acyl-CoA synthetase long-chain family member-4 (ASCL4), which initiates the formation of lipid peroxides, and divalent metal transporter-1 (DMT1), which increases redox-active iron, were upregulated in the Akita while downregulated in the Akita/MMP9KO hearts (Akita vs WT: ASCL4: +1.42-fold p<0.05, DMT1: +1.34-fold p<0.05; Akita/MMP9 vs Akita: ACSL4: -1.46-fold p<0.05, DMT1: -1.03-fold p<0.05). Furthermore, cardiac levels of Ferritin-Light Chain (FLC), which stores iron to suppress ferroptosis, was downregulated in the Akita but upregulated in the Akita/MMP9KO hearts (Akita vs WT: -2.01-fold p<0.01, Akita/MMP9 vs Akita: +1.36-fold p<0.05). These results suggest that upregulation of MMP9 promotes while inhibition of MMP9 mitigates ferroptosis in the T1DM heart. Conclusion: This is the first report to reveal MMP9 as a promising therapeutic target for T1DM-induced myocardial ferroptosis. This work was supported in part by the National Institutes of Health (NIH) Grant R56HL156806 to PKM, and University of Nebraska Medical Center (UNMC) Presidential Graduate Fellowship to FIG. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

The Effect of Acute and Chronic Hydration Changes on Vascular Aquaporin Expression

Introduction: The human body's homeostatic balance, particularly within cardiovascular function, relies heavily on adequate water intake to replenish losses from urine, sweat, feces, and respiration. The pressing issue is that a significant segment of the global populace lacks access to safe drinking water or faces inconsistent availability, a situation that is expected to worsen, heightening the urgency to understand water deprivation's physiological impacts. Dehydration, or hypohydration, manifests when water loss exceeds intake, with even minor instances compromising mental and physical health and correlating with detrimental cardiovascular consequences like hypertension, stroke, and coronary heart disease. While most research is focused on acute dehydration, chronic insuffcient water consumption, also known as underhydration, is also associated with similar negative effects on health. Despite this, the influence of acute and chronic water intake reduction on resistance-sized arteries and vascular smooth muscle cells (VSMCs), crucial in blood pressure regulation, remains inadequately explored. Aquaporins (AQPs) are membrane proteins facilitating cellular water transport, while the aquaglyceroporins (AQP3, AQP7, AQP9-10) subfamily also allows glycerol and other small solutes to permeate, are implicated in this process. While AQP7 function has been studied previously in the cardiovascular system, particularly its role in cardiac glycerol uptake, little is known regarding its function in systemic arteries that regulate blood pressure. Study Objective: The objective of this study is to understand the effects of dehydration and chronic reduced water intake on the expression of aquaglyceroporins, as well as resistance-sized arterial function, particularly in VSMCs, which are crucial for regulating systemic blood pressure. Hypothesis: The hypothesis is that dehydration will result in an elevation of the expression of glycerol-permeable aquaporins (AQP7 and AQP9) in resistance-sized artery VSMCs, elevating cellular glycerol content. Methodology: The study involves either inducing dehydration in C57BL/6J and AQP9−/− mice through water deprivation for 48 hours or restricting water intake for 28 days to investigate the expression of aquaporins (AQPs) in mesenteric arteries. In addition, the effects of glycerol supplementation (7 days ad libitum) and estrogen were also determined on AQP7 expression in male and ovariectomized female mice, respectively. Changes in message and protein expression were determined by RT-qPCR and Simple Western, respectively. Data: The data includes plasma osmolarity and glycerol concentration after 48 hours of dehydration, in C57BL/6J and AQP9−/− mice. Aquaglyceroporin expression levels were determined in mesenteric arteries following periods of dehydration, reduced water intake, and glycerol supplementation, in C57BL/6J and AQP9−/− mice. Summary of Results: Preliminary results indicate that water deprivation for 48 hours increases the expression of AQP7 in mouse mesenteric arteries, compared to controls, whereas 28 days of reduced water intake results in an elevation in AQP9 expression. Glycerol supplementation for 7 days, also results in elevated AQP7 expression levels, whereas, in contrast, AQP7 expression is not elevated in mesenteric arteries isolated from ovariectomized females. mice, with a concurrent increase in mesenteric artery glycerol content. AQP9−/− mice have higher plasma glycerol levels compared to controls, however, dehydration-mediated elevation in AQP7 expression is not attenuated by AQP9 KO. Conclusions: The study concludes that mice exhibit differential responses to short-term and long-term alterations in water intake, with changes in the expression of aquaglyceroporins in resistance-sized arteries, potentially increasing glycerol uptake into VSMCs providing an energy source during periods of water scarcity. This work was supported by American Heart Association AIREA grant number 947620. 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.

Hydrogen Sulfide Regulates Erectile Function through Stimulation of Antioxidant Defense in the Corpus Cavernosum

Hydrogen sulfide (H2S) is a gaseous cell signaling molecule with vasodilatory properties. Diminished H2S production has been implicated in the pathology of several cardiovascular diseases. H2S may protect against oxidative stress through scavenging of reactive oxygen species (ROS) or through stimulation of the Nrf2-mediated cellular antioxidant defense systems. We have previously demonstrated that mice fed a western diet for 12 weeks develop elevated penile ROS levels and impaired erectile function, which coincides with diminished corpus cavernosal expression of cystathionine γ-lyase (CSE), a major H2S producing enzyme. The objective of this study was to investigate the role of H2S in the regulation of erectile function and penile redox balance. We hypothesized that H2S levels will be positively associated with cellular antioxidant defense and erectile function. Young male C57Bl/6J mice (n = 120) were fed a control diet (CD) or western diet (WD) ad libitum for 18 weeks. For the final six weeks of the dietary intervention, half of the mice were switched to an equivalent diet containing the H2S pro-drug SG1002 at approximately 20 mg/kg/day. Separately, male CSE knockout mice (n = 26) and wild type (WT) littermate controls (n = 26) were fed a standard diet and studied at 6 months. Following the interventions, erectile function was assessed by measuring intracavernosal pressure (ICP) and mean arterial pressure (MAP) during cavernous nerve stimulation (1, 2, 4 V). In separate mice, penile in vivo ROS production was measured via microdialysis. Relative expression of 18 genes related to cellular antioxidant defense were assessed from naïve corpus cavernosum tissue by qRT-PCR. Group differences were determined by two-way ANOVA, with an α-level of 0.05. Erectile function was impaired in CSE KO mice (2V ICP/MAP - WT: 0.70±0.039 vs. KO: 0.55±0.043; p<0.05). Erectile function was similarly impaired in the untreated WD-fed mice (CD: 0.68±0.035 vs. WD: 0.49±0.012; p<0.05), while SG1002 induced a 54% functional restoration in WD mice (WD+SG1002: 0.59±0.019; p<0.05). Penile production of the ROS hydrogen peroxide and superoxide were elevated in CSE KO mice (WT: 0.73±0.04 vs. KO: 1.19±0.13; p<0.01). Penile ROS were also elevated in the WD mice (CD: 0.71±0.07 vs. WD: 1.09±0.15; p<0.01), which were normalized by SG1002 treatment (WD+SG1002: 0.83±0.07; p<0.01 vs. WD). Five antioxidant genes (Gclc, Gpx1, Gpx4, Prdx3, and Hmox1) that were stimulated by SG1002 treatment were also downregulated in CSE KO cavernosal tissues. Conversely, Txnip, a negative regulator of the thioredoxin antioxidant system was suppressed by SG1002 treatment and increased in CSE KO tissues. These results indicate that H2S is a key regulator of the cellular antioxidant systems and ROS balance in the penis, which may also regulate erectile function. Grant number K01DK115540 from 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.

MiRNA Regulation of Cerebrovascular Inwardly Rectifying K+ Channels During Onset of Alzheimer Disease: Role of Cholesterol and Cannabidiol Treatment

Currently, more than 6 million Americans live with Alzheimer disease (AD). Recent studies demonstrate that impaired blood flow in the brain is integral to the development of AD. Vascular inwardly rectifying K+ channels, such as KIR2.x and KIR6.x, are important for regulating vasoconstriction and vasodilation to tune cerebral perfusion in response to metabolic demand. We’ve previously identified that disruption in membrane cholesterol during advanced AD pathology restores function of KIR2.1 channels to that of young, healthy conditions or better. Additionally, we’ve identified specific microRNAs (miRNAs) in cerebral vessels that can be used to track early development of AD. In this study, we seek to understand molecular pathways stemming from miRNAs that directly or indirectly modulate activity of KIR2.x ( Kcnj2, Kcnj12) and KIR6.x ( Kcnj8, Kcnj11) channels. These ion channels are abundant in cerebrovascular endothelium and smooth muscle cells while particularly sensitive to dyslipidemia. We hypothesize that cerebrovascular miRNAs marking AD pathology are involved in dysregulation of inwardly rectifying K+ channels via cholesterol signaling. With employing QIAGEN’s Ingenuity Pathway Analysis (IPA), we first identified miRNAs that generally regulate each of the target genes for select KIR channels. With applying acquired knowledge of cerebrovascular miRNAs implicated in AD, we found which of these miRNAs also regulate cellular membrane cholesterol levels. Finally, we pinpointed miRNAs sensitive to cannabidiol (CBD) treatment during the development of AD as a potential therapeutic alternative to statins and cyclodextrins. In total, there are 233 miRNAs that regulate Kcnj2, 43 for Kcnj8, 203 for Kcnj11, and 177 for Kcnj12. When factoring in miRNAs that are AD-related, remaining miRNAs include nine that regulate Kcnj2, and one each for Kcnj8, Kcnj11, and Kcnj12. Remaining miRNAs that are cholesterol-related include one for Kcnj2, 43 for Kcnj8, 191 for Kcnj11, and one for Kcnj12. In general, at AD onset, CBD upregulates KIR2.2 and downregulates KIR2.1, KIR6.1, and KIR6.2 channels. CBD reversed expression of miRNAs involved in KIR2.x channel regulation in endothelial and smooth muscle/pericytes (e.g., miR-133 and miR-145) during AD onset in 3xTg-AD animals relative to wild-type controls. CBD also reverses expression of miR-129 and miR-151 to effectively upregulate genes modulating KIR6.x channels from onset of AD relative to wild-type. Altogether, we evidence specific pathways underpinning regulation of KIR2.x and KIR6.x channels in the transition from a healthy to diseased brain. This work was supported by the National Institutes of Health (R01AG073230). 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.

Skin Wetting Attenuates the Thermal Strain of Older Adults Exposed to Very Hot and Dry Heat with Accompanying Activities of Daily Living

Heat waves cause more deaths and hospitalizations in the elderly relative to any other age group. Indoor cooling with an air conditioner is an effective strategy to prevent the deleterious health effects of heat. However, air conditioning may not be available to some due to limited access, rising energy costs, power outages, and/or industry/government-imposed rolling blackouts. Thus, there is a clear need to identify non-air conditioning dependent cooling strategies to attenuate excessive elevations in body temperature and associated physiological strain in the elderly during heat wave conditions. Purpose: We tested the hypothesis that supplemental skin wetting via water spray attenuates elevations in core temperature and the accompanying physiological strain in older adults exposed to very hot and dry heat with accompanying activities of daily living. Methods: In a randomized order, 10 older adults (4 Females/6 Males; 74 ± 5 years) were exposed to 3-hours of ambient heating, replicating peak environmental conditions during the 2018 Los Angeles heat wave (47 ºC, 15% relative humidity), with (water spray) or without (control) skin-wetting via tap temperature water (~40 g applied every 10-minutes). To simulate heat generation associated with activities of daily living, participants performed six 5-minute periods of light exercise (~3 METS; metabolic heat production: 2.93 ± 0.42 W/kg in control and 2.95 ± 0.44 W/kg in water spray) dispersed throughout the heat exposure. To maintain euhydration, participants consumed 3 mL/kg/hr of tap-temperature water. We assessed core and skin temperatures, heart rate, whole-body sweat rate, and forearm blood flow (as a surrogate of changes in skin blood flow). We compared data between control and water spray trials using one-tailed paired t-tests. Results: When compared to control, water spray reduced the increase in core temperature by 0.33 ± 0.43 °C (p=0.020), ending skin temperature by 1.83 ± 0.73 °C (p<0.001), and ending heart rate by 6 ± 9 bpm (p=0.033). Whole-body sweat rate was 2.12 ± 1.08 g/min lower with water spray compared to control (p<0.001). However, the increase in forearm blood flow was not different between control (154 ± 74 mL/min) and water spray (149 ± 93 mL/min) trials (p=0.400). Conclusion: These preliminary data show that supplemental skin-wetting via water spray attenuates the thermal (core and skin temperature) and associated physiological strain (heart rate and fluid-loss) of older adults exposed to extreme heat with accompanying activities of daily living. The downstream impact of this reduced thermal strain on cardiac and renal stress should be examined, as these are two of the main causes of heat-related morbidity and mortality. Supported by NIH R01AG069005 (CGC) and AHA 23POST1023065 (ZJM). 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.

Loss of Htr1B Leads to a Failure in the Neonate Autoresuscitation Reflex

Sudden Infant Death Syndrome (SIDS) is the leading cause of death in infants under the age of 1, with an unknown etiology, that takes the lives of 3,400 infants per year in the US alone. Interestingly, SIDS cases show males predominance (60%), however this sexual disparity in is not fully understood. SIDS is believed to follow a triple risk hypothesis model where the infant has an innate vulnerability, is at a critical developmental period, and is challenged with an exogenous stressor. A leading hypothesis indicates many SIDS cases are mechanistically driven by a failure in the autoresuscitation reflex. The autoresuscitation reflex is a series of gasps that occur to revitalize normal cardiorespiratory function when an infant falls into a hypoxic coma, characterized by an apnea and bradycardia, due to severe hypoxic conditions (i.e., rebreathing while sleeping in face down or with the face blocked). Although the cause of failure in the autoresuscitation reflex for SIDS remains unknown, post-mortem studies have found abnormalities related to the central serotonin (5-HT) neurotransmitter system, including several 5-HT receptors (5-HTr’s). Follow up studies in animal models show that 5-HT system perturbations result in a significant survival decrease in neonatal animals during anoxic (3% CO2/balance N2) gas challenges that test the autoresuscitation function, including pharmacological receptor manipulations. Furthermore, adult animal studies report that 5-HT receptor stimulation alters various respiratory parameters (i.e., tidal volume, respiratory rate, gasping). What remains to be understood is the cellular and molecular mechanisms through which 5-HT plays a role in the autoresuscitation reflex and how those mechanism may be disrupted in SIDS. We hypothesize that Htr1B is required for successful autoresuscitation. To test this hypothesis, we utilized an automated closed loop robotic platform for neonate cardio-respiratory measurements ( Looper) to assay P7 Htr1B loss of function mice for their abilities to survive repeated anoxic gas challenges testing the autoresuscitation reflex. Using Looper, we find that the loss of Htr1B decreases survival to repeated anoxic challenges compared to wild type (WT) controls in both male and female mice. Additionally, a subset of male heterozygous Htr1B mice survive fewer challenges compared to WT mice, whereas others survive a similar number of challenges as WT mice; a phenotype not observed in female mice. Our data supports the hypothesis that modulations to the serotonin system via Htr1B is important in eliciting the autoresuscitation response. Future studies aim to investigate additional respiratory parameters from respiratory trace data, in addition to recovery parameters, and functionally mapping out where in the brainstem and what neuronal populations require the expression of this receptor for the autoresuscitation reflex. R01 HL161142. 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.

MyoD Over-expression Reprograms Elephant Seal Fibroblasts into Muscle Cells

Ex vivo tissue culture allows the study of complex cellular mechanisms that are relevant to physiological responses while overcoming the challenges presented by studying animals that are not tractable. In a primary cell culture system, certain proliferating cells can be functionally reprogrammed into other cell types via overexpression of key genes. Dermal fibroblasts can theoretically be reprogrammed into muscle cells, which are often challenging to obtain from wild organisms but offer a unique system to study metabolic responses, by overexpression of the myogenic transcription factor myoD. We derived primary dermal fibroblasts from Northern elephant seal (NES) skin samples and propagated them in primary culture. NES cells respire, stain positive for fibroblast markers (vimentin and PDGFR), and are amenable to electroporation. We overexpressed GFP-myoD in NES fibroblasts and conducted antibiotic selection and purification by FACS. As expected, expression of myoD was higher in transfected cells than in controls according to qPCR analysis (t-test p< 0.05). Treatment with small molecules (CHIR99021, Forskolin and Repsox) enhanced myoD expression. Furthermore, fibroblasts overexpressing myoD also expressed downstream myogenenic markers (myogenin, myosin heavy chain 1 and myosin heavy chain 8). MyoD-overexpressing cells differentiate into myotubes, become multinucleated and stain positively for myosin heavy chain 1. RNAseq analysis confirmed a transcriptional profile of myoD expressing cells, which is unique and different from the naive dermal elephant seal fibroblasts. Establishing differentiated muscle fibers from other mature cell types could provide a unique platform to conduct mechanistic studies in species where muscle tissue samples cannot be obtained from live animals. The Department of Defense National Defense Science and Engineering Graduate (NDSEG) 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.

Cold-water foot immersion and physiological strain of adults with coronary artery disease during hot and humid heat exposure

Introduction: Heat extremes are associated with a greater risk of adverse cardiovascular outcomes, especially among adults with coronary artery disease. While air-conditioning provides exceptional protection during heat extremes, it is neither sustainable nor widely accessible. Cold-water foot immersion reduces physiological heat strain in healthy young adults but its effect in more vulnerable populations remains unknown. Objective and hypotheses: This study aims to identify the effect of cold-water foot immersion on markers of physiological heat strain in adults with coronary artery disease. We hypothesized that cold-water foot immersion would reduce physiological heat strain when used on its own and that this effect would be greater when combined with an electric fan. Methods: 17 adults living with stable coronary artery disease (2 females/15 males; 67±8 years) were exposed to a 38°C, 60% relative humidity environment for 3 hours on three separate, randomized occasions: i) no cooling (control; CON); ii) cold-water foot immersion (20 min of immersion each 30 min, ~30 cm in water kept at ~18°C; FI); iii) cold-water foot immersion and fan use (FI+FAN). Rectal and skin temperatures, heart rate (5-lead ECG), and whole-body sweat loss (change in nude weight) were measured. Results: The increase in rectal temperature did not differ between conditions (CON: 0.40±0.24°C, FI: 0.41±0.29°C, and FI+FAN: 0.36±0.22°C; p≥0.49). The increase in skin temperature was reduced with FI and FI+FAN compared to CON (CON: 4.9±0.8°C, FI: 4.1±1.2°C, and FI+FAN: 4.3±0.8°C; p≤0.01), with no difference between FI and FI+FAN (p=0.15). Similarly, the increase in heart rate was reduced with FI and FI+FAN compared to CON (CON: 8±6 bpm, FI: 4±6 bpm, and FI+FAN: 3±6 bpm; p≤0.01), with no difference between FI and FI+FAN (p=0.45). Sweat loss was also reduced by FI and FI+FAN compared with CON (CON: 823±114 g, FI: 544±174 g, and FI+FAN: 671±255 g; p≤0.03), with sweat loss during FI sweat loss being lower than during FI+FAN (p=0.03). Conclusion: The results show that cold-water foot immersion, used alone or in combination with an electric fan, reduces the increase in heart rate and whole-body sweat loss of adults living with coronary artery disease exposed to a hot and humid environment for 3 hours. This could be linked to the lower increase in skin temperature with foot immersion. National Health and Medical Research Council of Australia (APP1147789). 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.

Chronic Hyperoxia Augments the Hypercapnic Ventilatory Response in Adult Rats

Rats exposed to 4 – 14 days of 60% O2 as adults exhibit a modest enhancement of their hypoxic ventilatory response (HVR) (Danielson & Bavis, Physiology 38(S1): 5730119, 2023). To determine whether this plasticity is unique to the HVR or a general increase in excitability of the respiratory control system, we tested the hypothesis that chronic hyperoxia would also enhance the hypercapnic ventilatory response (HCVR). The ventilatory response to 7% CO2 was measured by whole-body plethysmography in adult, Sprague-Dawley rats immediately after 4 and 14 days of exposure to 60% O2 or an equivalent time period in room air. Baseline ventilation and the HCVR were unchanged after 4 days of hyperoxia. The HCVR was increased after 14 days (Treatment × FICO2, P=0.004), with hypercapnic ventilation being approximately 15% greater than in control rats. However, this effect was no longer significant after accounting for variation in metabolic rate, and the HCVR was fully recovered when rats were restudied four weeks after they were returned to room air. In a follow-up experiment, pulse oximetry was performed in isoflurane-anesthetized rats breathing room air or 12% O2. Exposure to 4 – 14 days of 60% O2 did not impair gas exchange, so augmented ventilatory responses likely reflect changes in the neural control of breathing and/or metabolism rather than differences in the levels of hypoxemia and hypercapnia experienced by rats during the tests. In conclusion, chronic hyperoxia elicits plasticity in both the HVR and HCVR of adult rats, but these responses recover in less than one month after rats are returned to room air. Supported by NIH grant P20 GM-103423 (Maine INBRE). 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.

Effects of Cytotoxic Chemotherapy and Endocrine Therapy on Hemodynamics and Oxygen Uptake During Handgrip Exercise in Patients Treated for Breast Cancer

Breast cancer therapies can alter skeletal muscle blood flow during exercise and decrease mitochondrial content and function. However, the impact of different therapies on the variables determining oxygen transport and utilization during submaximal exercise remain unknown. We tested the hypothesis that both chemotherapy and endocrine therapy would decrease blood flow and increase deoxygenated [hemoglobin+myoglobin] (HHb) with an unchanged oxygen uptake (VȮ2) during exercise compared to healthy controls. Participants were healthy females (CTRL; n = 5; age: 58 ± 8 years; body mass index: 25 ± 4 kg/m2) or female patients diagnosed with stage I-III breast cancer comprising three groups: 1) two to five weeks post completion of cytotoxic chemotherapy (CHEMO; n = 5; age: 55 ± 8 years; body mass index, BMI: 30 ± 4 kg/m2); 2) currently on endocrine therapy ≥5 months (ENDO; n = 9; age: 59 ± 7 years; BMI: 27 ± 6 kg/m2); and 3) completed cytotoxic chemotherapy and currently on endocrine therapy ≥5 months (CHEMO+ENDO; n = 8; age: 58 ± 6 years; BMI: 26 ± 5 kg/m2). Forearm blood flow, HHb, and estimated VȮ2 were measured during the final minute of a 3-minute intermittent isometric handgrip exercise at 3 and 6 kg. There were no group or group x intensity effects (all p<0.18) for forearm blood flow (CTRL: 260 ± 33 ml/min; CHEMO: 407 ± 96 ml/min; ENDO: 309 ± 140 ml/min; CHEMO+ENDO: 313 ± 86 ml/min), HHb (CTRL: 134 ± 58 μM; CHEMO: 73 ± 36 μM; ENDO: 118 ± 67 μM; CHEMO+ENDO: 101 ± 25 μM), or estimated VȮ2 (CTRL: 59 ± 28 ml/min; CHEMO: 48 ± 21 ml/min; ENDO: 54 ± 28 ml/min; CHEMO+ENDO: 53 ± 21 ml/min). These findings indicate that chemotherapy and endocrine therapy do not affect muscle hemodynamics and oxidative metabolism during submaximal handgrip exercise. This study was funded, in part, by the Veterans Affairs Clinical Science Research and Career Development Award (IK2 CX002114). 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.

Protein Kinase C Beta II Inhibitor Conjugated with Myristic Acid and Trans-Activator of Transcription improves intracellular delivery and cardiovascular protection in porcine myocardial ischemia/reperfusion injury

Introduction: While timely reperfusion of oxygenated blood is critical during resuscitation of ischemic myocardium, oxidative stress during reperfusion still leads to ischemia/reperfusion (I/R) injury and ultimately, cardiomyocyte death. The major sources of oxidative stress targeted in this study are NADPH oxidase (NOX-2) and mitochondria, which are both activated by protein kinase C beta II (PKCβII). In previous studies with an ex-vivo rat heart I/R model, Myristic Acid (Myr) and Trans-Activator Transcription (Tat; YGRKKRRQRRR) conjugated PKCβII inhibitor (Myr-Tat-PKCβII-; N-Myr-Tat-CC-SLNPEWNET) showed cardioprotective effects and decreased infarct size. In this study, we hypothesized that Myr-Tat-PKCβII- will offer cardioprotective effects in comparison with a scrambled peptide control (Myr-Tat-PKCβII-scram; N-Myr-Tat-CC-WNPESLNTE) in an in-vivo porcine myocardial I/R model. Methods: Regional I(1 hour)/R(3 hours) was induced in Male Yorkshire pigs (38-50kg) by inflating a balloon to occlude the Left Anterior Descending Artery (LAD) at the level of the second diagonal branch (supplies 40% of anterior left ventricle) and then deflating it to allow for reperfusion. Then, a bolus of either Myr-Tat-PKCβII- or Myr-Tat-PKCβII-scram (20ng/kg; ~100pmol in blood) was immediately administered into the LAD. Cardiac function and injury were measured by monitoring changes in ejection fraction (EF) and through routine measurements of serum creatine phosphokinase (CPK), troponin I, and myoglobin, respectively. After I/R, the hearts were stained with 1% Evans Blue dye to identify the area at risk (AR) and 1% triphenyltetrazolium chloride to determine the area of necrosis (AN). Infarct size was then quantified (AN/AR) and all data was analyzed via Student’s t-test. Results: Analysis showed that Myr-Tat-PKCβII- significantly restored EF to within 1.40.7% of baseline compared to controls which only restored EF to within 6.42.1% (p<0.05) of baseline EF. Myr-Tat-PKCβII- showed a significant increase in serum myoglobin levels at 1 hr of reperfusion (1362.1 83.4 μg/mL, n=4) compared to scrambled control (202.1197.3 μg/mL, n=3 p<0.05). Myr-Tat-PKCβII- reduced infarct size to 10.0±2.8%; n=4; compared to scrambled control hearts (28.5±8.3%; n=6; p<0.05). CPK and Troponin I levels were comparable in both groups. These results suggest that Myr-Tat-PKCβII- can help prevent cardiac injury when given immediately after an ischemic event. Conclusions: Data from ex-vivo rat heart I/R model, coupled with data from this in-vivo porcine myocardial I/R model indicate the effcacy of Myr-Tat-PKCβII- in preventing oxidative stress-induced myocardial I/R injury when given at the beginning of reperfusion. These findings suggest that Myr-Tat-PKCβII- could be useful in the clinical setting when administered immediately after cardiac resuscitation. Future studies include the treatment of rat cardiomyocyte cells with Myr-Tat-PKCβII- prior to 24 hr hypoxia/24 hr reoxygenation, followed by cell viability assays compared to untreated control. This additional data can help determine the optimal dose to use in a 12 week survival study using the same porcine myocardial I/R protocol. Funding: This study was funded by the Philadelphia College of Osteopathic Medicine, Department of Biomedical Sciences, Division of Research, and the Center for Chronic Diseases of Aging, the National Heart, Lung & Blood Institute at NIH (grant # 1R43HL160338-01) and Young Therapeutics, LLC. 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.

B1AR regulation of the Cav1.2 via the SAP97 complex

Beta adrenergic (BAR) signaling is stimulated by the catecholamines norepinephrine (NE) and epinephrine (EPI) to control cardiac contractility. The beta-1-AR (B1AR) is the major cardiac subtype. B1AR signals canonically through the Gas subunit, leading to increases in cAMP and PKA; however, it can also signal via the Gai subunit, leading to increased NOS1, cGMP, and PKG levels. B1AR-NOS1 signaling leads to increased contractility and calcium cycling in cardiomyocytes. We found a novel complex within cardiomyocytes in which the B1AR, Cav1.2, and NOS1 proteins are held in proximity by the membrane scaffolding protein SAP97. In heart failure, there is a decrease in SAP97 expression and impaired B1AR signaling. Cardiac-specific deletion of SAP97 disrupts this complex. In the SAP97-cKO mice, there are minimal changes in B1AR-Gas; however, B1AR-Gai signaling is decreased, with a loss of B1AR-NOS1 signaling. Furthermore, we see a decrease in whole cell calcium currents and cardiac contractility. In mice lacking the NOS1, we see the same decrease in calcium currents. We hypothesize SAP97 is necessary to maintain B1AR modulation of Cav1.2 in cardiomyocytes. Using electrophysiology and biochemical techniques, we aim to elucidate the role of SAP97 in B1AR modulation of Cav1.2 and how this is impacted by the impairment of B1AR-Gai signaling. T32HL086350 RO1-HL147263. 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.

Effects of Cross-Sex Hormone Therapy on Metabolic Parameters and Aortic Relaxation in Castrated Male Rats

With the rising awareness, the number of individuals identifying themselves as transgender in the US is increasing over the years. Cross-sex hormone therapy (CSHT) may alter numerous cardiometabolic parameters leading to the increased risk of cardiovascular diseases (CVD) in transgender population. Epidemiological studies suggest that transgender females (male to female, MtF) on estrogen therapy develop higher risk of CVD compared to transgender males (female to male, FtM) taking testosterone. Underlying mechanisms of impaired cardiovascular functions in MtF are not well documented. This study was undertaken to examine the effects of 17β-estradiol (E2) on certain cardiometabolic parameters and aortic reactivity in castrated (CAS) male Sprague Dawley (SD) rats. The 8-10-weeks old CAS rats were subcutaneously implanted with either 1.5 mg of E2 (CAS+E2) or placebo (CAS+PL) containing pellets for ~35 days. The age-matched SD intact male (IM) rats were also included in the experimental groups. After performing the glucose tolerance test, animals were sacrificed, and the blood was collected for later measurements of the HbA1C and triglyceride (TG) levels. Endothelium-dependent vasorelaxation (EDV) to acetylcholine (ACh) in aortic rings pre-contracted with phenylephrine (PE) was measured before and after treatment with indomethacin (a cyclooxygenase inhibitor), followed by L-NAME [a nonselective nitric oxide (NO) synthase (NOS) inhibitor]. Contractile responses to PE before and after L-NAME in aortic rings and sodium nitroprusside (SNP)-induced relaxation responses in endothelium-denuded rings were also measured. Here, we report the decreased body weight and visceral white adipose tissue, and improved HbA1C and glucose tolerance in E2-treated CAS rats. However, the E2-treated CAS rats exhibited elevated plasma level of TG. Furthermore, the vascular relaxation to ACh was significantly impaired in aortas from this group compared to those in CAS+PL and IM rats. The impairment of ACh responses in CAS+E2 rats was accompanied by a significant decrease in NO contribution to ACh vasorelaxation. The basal NO levels and the smooth muscle sensitivity to NO were not altered, whereas the maximum contractile responses to PE were enhanced in aortas of CAS+E2 group compared to IM. In conclusion, our data suggests that the glucose homeostasis was improved in CAS+E2 rats. Regardless, this group exhibited increased level of TG in plasma and decreased aortic vasorelaxation to ACh. The impairment of EDV in E2-treated CAS rats might be due to reduced NO-mediated vasorelaxation or increased contractile responses observed in this group. Additional studies are needed to document the underlying mechanisms for improvement of glucose homeostasis and impairment of EDV in CAS+E2 rats. NIDA/NIGMS, 1SC1DA052120-01 to MF and Bridge Grant from University of the Pacific to RR. 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.

Gut-muscle axis: establishing the connection between microbial signaling and skeletal muscle function in a mouse model (mdx) of Duchenne muscular dystrophy

The metabolic and endocrine nature of skeletal muscle allows for systemic signaling and influence over the enteric environment influencing gut microbial populations. Concomitantly, commensal microbial signaling can alter the composition and development of skeletal muscle forming a bidirectional gut-muscle axis. Duchenne muscular dystrophy (DMD) is a fatal neuromuscular disease characterised by skeletal muscle atrophy, fibrosis, and ultimately cardiorespiratory failure. Previous studies have shown that gut microbial signaling can alter the pathways involved in muscle atrophy, enhancing atrophy when dysbiotic, or blunting the atrophic effect by restoring gut microbial populations to a healthy status; thus, we sought to characterize the metabolic signaling between the gut and the diaphragm in a mouse model of DMD ( mdx) to identify potential therapeutic targets. The study was divided into two arms and conducted following institutional ethical approval. The first arm investigated metabolomic signalling. 6-month-old male BL10 wildtype (WT; n = 12) and mdx (n = 12) mice were anaesthetized (induction by 5% isoflurane) and decapitated. Following collection of trunk blood, the diaphragm was excised, and colonic/cecal contents were collected. The samples were then processed by mass-spectrometry to isolate the metabolomic profiles of semi-polar, secondary bile acid, and short chain fatty acid (SCFA) targets in the gut, plasma and diaphragm of WT and mdx mice. The second arm of the study explored the gut microbial profile and diaphragm gene expression, structure and function. 6-month-old male WT (n = 15) and mdx (n = 15) were anesthetized (induction by 5% isoflurane) followed by cervical dislocation. The diaphragm was excised, and longitudinal strips were isolated for structural analysis (i.e., histological staining and immunohistochemistry for fibre type and size), PCR gene expression, and isometric force assessment ex vivo. Additionally, faecal pellets were collected and analysed via shotgun metagenomic sequencing to assess microbial populations. Diaphragm twitch and tetanic force in mdx were profoundly decreased compared to WT. Metabolic analysis of faecal metabolites indicated impairment in the three main tryptophan metabolic pathways in mdx mice: kynurenine, indole and serotonin. Metagenomic analysis indicated a profound genotype effect between WT and mdx gut microbial populations. Two main producers of the short chain fatty acid acetate (Lactobacillus and Bifidobacterium) were significantly decreased within the mdx group. Acetate serves as a substate in the TCA cycle contributing to ATP production and positively affects skeletal muscle via numerous pathways including the down regulation of key atrogenes associated with atrophy. Pathway enrichment analysis showed a global disruption to both purine and pyrimidine metabolism in all three tissue types. Purine/pyrimidine metabolism have been tightly linked with microbial metabolism and affect skeletal muscle health and function. Further understanding of the gut-muscle axis in dystrophic models may pave the way for novel microbiota-directed therapeutic strategies to ameliorate muscle dysfunction in DMD. Funded by Science Foundation Ireland SFI/19/6628 INSPIRE DMD. 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.

SARS-CoV-2 Decreases Neuronal Activity in Brainstem Respiratory Centers in C57BI6/J Mice

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also called COVID-19, targets the respiratory system, leading to symptoms such as cough, fever, and diffculty breathing. As the mechanisms behind SARS-CoV-2 infections continues to be studied, understanding of how this virus targets specific tissues becomes more apparent. Angiotensin-converting enzyme-2 (ACE2), the target of SARS-CoV infections and a functional receptor for SARS-CoV-2 invasions, is highly expressed in many tissues throughout the body, including the lungs, kidneys, and brain. Notably, our group previously reported that neurons are the main cells within the brain expressing ACE2. Accordingly, we hypothesized that neuronal infection of brainstem respiratory centers by SARS-CoV-2 could contribute to respiratory symptoms associated with COVID-19, specifically respiratory failure. C57BI6/J mice were mock infected or received SARS-CoV-2 (7.5x103 or 1.5x104) intranasally in a BSL-3 facility (University of Texas in Galveston) and were euthanized by CO2 hypoxia after 5 days post infection. The heads were harvested and immersed in formalin for 3 days before being transferred to LSU Health-NO for processing. Brains were carefully dissected out and preserved in optimal cutting temperature (OCT) before sectioning on a cryostat. Sections (30 μm) containing the retrotrapezoid nucleus (RTN) were selected as its neurons are part of the pontomedullary regions that generate the respiratory rhythm and pattern. Immunohistochemistry for c-Fos, a marker of neuronal activity, was used to assess neuronal activity in the RTN. Sections were incubated overnight with a primary monoclonal antibody (rabbit anti c-Fos, 1:1000) followed with a secondary goat antirabbit fluorescent IgG (GFP, 1:200, 1h) antibody. Sections were then mounted to slides in the dark to preserve the fluorescence and observed under the microscope. Images of neurons present in the RTN were captured and neurons were then hand counted and averaged. Neuronal activity in the RTN was decreased with the dose of SARS-CoV-2 used to infect cells in the brain. The greater the dose of SARS-CoV-2, the lower the number of c-Fos-positive neurons was detected in the RTN. Mock brains had the greatest number of neurons and brains infected with 1.5x104 SARS-CoV-2 had the lowest number of neurons in the RTN. This was demonstrated by counting neurons at 3 different intervals and taking the average. We conclude that SARS-CoV-2 targets neurons in respiratory centers, possibly contributing to impaired respiratory function in infected patients. NIH/NHLBI HL163814. 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.

Endothelin-1 Receptor Antagonism Attenuates Increased Uncoupling Protein-1 in Brown Adipose Tissue of Obese Mice

Endothelin-1 (ET-1) is increased in patients and rodent models with obesity and promotes metabolic syndrome by causing inflammation and adipocyte dysfunction. Recently, our laboratory demonstrated that treatment of obese mice with Atrasentan (Atr) and Bosentan (Bos) significantly improved fasting blood glucose, insulin, and glucose and insulin tolerance; however, the mechanisms are not completely understood. Brown adipocytes express all components of the ET-1 system and are important in limiting adiposity though an increase in uncoupling protein-1 (UCP-1) leading to increased metabolism via thermogenesis. We hypothesized that ET-1 antagonism may improve metabolism in obese mice by regulating UCP-1 in brown adipose. Mice were fed either normal (NMD) or high fat diet (HFD) for 10 week and treated with either vehicle, Atr, or Bos for the final two weeks. HFD significantly increased ET-1 and tumor necrosis factor alpha expression in brown adipose tissue compared to NMD controls with no significant effect of either ET-1 receptor antagonists. Interestingly, brown adipose expression of UCP-1 was significantly increased in HFD fed mice compared to NMD, an effect that was significantly attenuated in mice treated with atrasentan and bosentan. These data suggest that ET-1 modulates brown adipose tissue function in obesity, a potential contributor to obesity induced cardio metabolic risk. This work was supported by National Institutes of Health grant 5T32HL105324-14. 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.