bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deletion of myostatin resolves obesity-induced myosteatosis and sarcopenia and improves angiogenesis in obese mice
Authors: Guilfoyle-Speese Andrew , Padgett Caleb , Bridgewater Cody , Corley Zachary , Mintz James , Fulton David , Stepp David 
Published: May 2023

Objective: To test the hypothesis that restored muscle mass achieved through deletion of myostatin improves angiogenesis in obese mice through the resolution of myosteatosis. Methods: db/db mice, a well-described model of obesity, were crossed with mice lacking myostatin (MSTN KO), a myokine that negatively regulates muscle differentiation and growth, or stearoyl Co-A desaturase 1 (SCD1 KO), the rate limiting enzyme for oleate synthesis and subsequent triglyceride production, to generate db +/-_MSTN +/- and db +/-_SCD1 +/- mice. We utilized confocal and nuclear magnetic resonance (NMR) spectroscopy to assess skeletal muscle (SKM) histology and morphology in db +/-_MSTN +/- and db +/-_SCD1 +/- mice. Muscle lipid content was analyzed via mass spectrometry. Femoral artery ligation was used to stimulate in vivo angiogenesis in response to ischemia; whereas, 1mm aortic rings cultured in ECBM (2% FBS) were used to study ex vivo angiogenesis. Gene expression was assessed by RNA-Seq with protein expression follow-up in isolated gastrocnemius SKM via RT-qPCR and western blotting. Results: As previously described, MSTN deletion results in significantly increased muscle mass without altering whole-body mass or fat percentage in obese db/db mice. Additionally, we observed that obesity inhibits and MSTN deletion restores angiogenesis in both hind limb ischemia and aortic ring assay models. Despite persistent plasma lipedema, ectopic lipid deposition in SKM (Myosteatosis) was largely ameliorated in obese mice lacking MSTN, a reduction largely explained by a decrease in tissue triglyceride levels. Confocal microscopy revealed the accumulation of lipid in obese mouse myocytes that was lacking in obese mice with MSTN KO. RNA-Seq analysis of SKM exposed marked upregulation of lipogenesis pathways, notably the expression of SCD1. SCD1 was elevated at both the protein and RNA levels in db -_MSTN + SKM but not in db -_MSTN - SKM. Similar to MSTN KO, confocal imaging reveals that SCD1 deletion reverses lipid accumulation in obese mice. Conclusion: In summary, restored muscle mass in obese mice provides potent protection to vascular and metabolic health. A potential correlate of this improvement is the resolution of myosteatosis in obese MSTN KO mice. These data suggest that resolution of myosteatosis, independent of muscle mass, may afford similar protection, possibly by targeted deletion or blockade of SCD1. A. C. Guilfoyle-Speese is supported by Kirschstein National Research Service Award (NRSA) Institutional Research Training Grant (T32) T32HL155011. D.W. Stepp and D.J. Fulton are supported by NIH 1R01HL147159. 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.
Transcription factor HNF4A activity is suppressed by microbiota and inhibits IFN beta production
Authors: Tillman Matthew , Lickwar Colin , Soderblom Erik , Horner Stacy , Rawls John 
Published: May 2023

Intestinal epithelial cells (IECs) separate the intestinal lumen from lamina propria resident immune cells, positioning IECs as mediators of microbial signals to the immune system. Understanding these microbe-IEC-immune interactions may represent potential therapeutic targets for immunological diseases. We previously discovered that microbiota regulate the activity of the nuclear receptor transcription factor Hepatocyte nuclear factor 4 alpha (HNF4A). Microbiota suppress HNF4A-activated genes in zebrafish and lead to genome-wide reduction of HNF4A DNA occupancy in mouse IECs. HNF4A activates lipid metabolism and epithelial differentiation gene programs, while also suppressing inflammatory and immune response gene programs in the intestine. We therefore hypothesized that microbial suppression of HNF4A contributes to activation of immunological pathways. We conducted an unbiased coimmunoprecipitation-mass-spectrometry analysis comparing HNF4A interacting partners in IECs from germ-free and conventionalized (germ-free mice colonized with SPF feces for 2 weeks) mice. HNF4A interacted with significantly more proteins in germ-free IECs, including several proteins involved in promotion of transcription and chromatin regulation, consistent with HNF4A being more active in germ-free mice. Our HNF4A and H3k27ac ChIP-seq data from IECs derived from germ-free and conventionalized mice identified that HNF4A binds ubiquitously to IEC enhancers, but also revealed a small number of enhancers that were activated by microbiota with no HNF4A binding. Motif enrichment analysis showed that these enhancers were enriched for binding sites for Interferon regulatory factors (IRFs). This raises the interesting possibility that there is a selective disadvantage to colocalizing IRF and HNF4A occupancy at a given enhancer, and suggests that these transcriptional regulatory pathways may otherwise communicate. To test this, we used a luciferase reporter assay in HEK293T cells to probe the impact of HNF4A on the IFNβ promoter, which is controlled by IRF3/7. HNF4A potently suppressed IFNβ promoter activity following viral stimulation. HNF4A DNA-binding activity is necessary for this suppression; however, there is no evidence HNF4A binds the IFNβ promoter, suggesting HNF4A likely induces a repressor of the IFNβ promoter. Together these results indicate that HNF4A is both a target of microbiota suppression and a potent suppressor of IFNβ production. Though IRF bound enhancers appear to be insulated against HNF4A binding in IECs, our results show that these two transcriptional pathways communicate, potentially representing a novel mechanism through which microbiota influence innate immunity. NIH P01-DK094779 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.
Vagal Afferent Innervation of the Atria and Ventricles of the Rat Heart: Anterograde Tracing
Authors: Chen Jin , Cheng Zixi 
Published: May 2023

Vagal afferent innervation of the atria from the nodose ganglion has been shown in previous studies but the innervation of the ventricles remains unknown. In this study, tracer Dextran-Biotin was injected into the left nodose ganglion of SD male rats (n=6; 3 months). The tracer was allowed to transport for 14 days, then the rats were perfused through the left ventricle with 40°C phosphate-buffered saline (PBS, 0.1 M, pH = 7.4). Tissues were then fixed by perfusion with 4% paraformaldehyde in 0.1M PBS (4°C, pH 7.4). Whole rat hearts were harvested, and the atria and ventricles were separated. Then, a cut was made along the interatrial septum to separate the left and right atrium, then either a DAB staining or fluorescent immunohistochemistry staining was performed. Intrinsic cardiac ganglionic (ICG) neurons were stained with Cuprolinic Blue or Fluoro-Gold. Labeled single vagal afferent axons in the flat mounts of the whole heart were traced using the Neurolucida system. Consistent with previous findings using fluorescent tracer 1,1’-dioleyl-3,3,3’,3’ tetramethylindocarbocyaninemethanesulfonate (DiI) injection, afferent axons have been observed in the epi-, myo-, and endocardium and vagal axons formed “flower-spray” and “end-net” terminals in the atria. Also, the afferents displayed contact with cardiac muscles. For the first time, the “flower-spray” and “end-net” vagal afferent terminals have been found in both the left and right ventricles. Neither the “flower-spray” and “end-net” vagal afferent terminals on the heart, nor the vagal afferent terminal structures on the stomach such as intraganglionic laminar endings ( IGLEs) and intramuscular arrays ( IMAs) were found to co-localize with calcitonin gene-related peptide (CGRP) or Substance P (SP) in the three rats with injection followed fluorescent labeling and immunohistochemical analysis. In conclusion, our study provides the foundation for further functional studies of vagal afferent innervation of the whole heart (atria and ventricles) in normal and pathological states. This study was supported by NIH HEAL/SPARC U01 NS113867-01 (ZJC), NIH R15HL137143-01A1 (ZJC). 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.
Inhibition of Histone 3 Lysine 4 Histone Methyltransferase Attenuates DOCA-Salt-Induced Hypertension
Authors: Cooper Silvana , Earley Yumei 
Published: May 2023

Emerging evidence suggests that epigenetic regulatory mechanisms contribute to the development of hypertension. However, whether there is significance of epigenetics on neurogenic hypertension development is not fully understood. We previously reported an elevation of Histone 3 Lysine 4 (H3K4) trimethylation in the paraventricular nucleus of the hypothalamus (PVN). Accordingly, we hypothesize that H3K4 histone methyltransferase (HMT) in the PVN contributes to the development of DOCA-salt hypertension. To test our hypothesis, C57Bl/6J mice were implanted with SHAM or DOCA (50mg) pellets and given free access to water or saline (0.9% NaCl) respectively for 3, 7, or 21 days. H3K4 HMT activity were assessed in the PVN (n = 3-5 mice/group) and expressed as fold change. The HMT activity in the PVN was increased as early as 3 days after DOCA-salt compared with SHAM (6.1 ± 0.69 vs. 1.0 ± 0.73, P < 0.05), remained elevated at day 7 (6.3 ± 1.29 vs. 1.0 ± 0.90, P < 0.05) and day 21 (1.6 ± 0.07 vs. 1.0 ± 0.07, P < 0.05) of DOCA-salt treatment compared with SHAM. To examine the contribution of HMT activity to the development of DOCA-Salt hypertension, another cohort of mice (n = 3-5 mice/group) were implanted with telemetry transmitters to mornitor the blood pressure. After 10 days of recovery, mice treated with DOCA-Salt salt and intracerebroventricularly (ICV) infused with either artificial CSF or 5'-methylthioadenosine (MTA), a H3K4 HMT inhibitor, for 21 days. Importantly, ICV infusion of MTA attenuated mean arterial pressure (123.1 ± 6.3 vs. 138.5 ± 7.4 mmHg, P<0.05) compared with the control following DOCA-salt treatment. In addition, ICV infusion of MTA significantly reduced the H3K4 HMT activity (1.0 ± 0.08 vs 1.7 ± 0.07, P < 0.05) compared with aCSF group following 21 days of DOCA-salt treatment confirming the effectiveness of the inhibitor. In summary, these findings suggest the importance of elevated HMT activity in the PVN in DOCA-salt-induced hypertension. Further studies will be performed to identify the downstream targets of HMT and the mechanisms involved. R01HL122770, 1P20GM130459, R35HL155008-01S1 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.
The substantia nigra modulates proximal colon tone and motility in a vagally-dependent manner in the rat
Authors: Xing Tiaosi , Nanni Giorgia , Burkholde Cameron , Browning Kirsteen , Travagli R. Alberto 
Published: May 2023

Previous studies have shown that a monosynaptic pathway connects the substantia nigra pars compacta (SNpc) to neurons of the dorsal motor nucleus of the vagus (DMV). This monosynaptic pathway modulates the vagal control of gastric motility. The present study was designed to test the hypothesis that this nigro-vagal pathway also modulates the tone and motility of the proximal colon.In rats, concurrent microinjection of a retrograde tracer in the proximal colon and an anterograde tracer in the SNpc (n=4) showed that bilaterally labelled colonic-projecting preganglionic vagal motoneurons in the DMV received inputs from SNpc neurons. Activation of SNpc neurons via microinjection of the ionotropic glutamate selective agonist, NMDA, increased proximal colonic motility (187±52.6% of baseline, n=13) and tone (323±97.2mg, n=14) as measured via a strain gauge aligned with the colonic circular smooth muscle (paired t test, p<0.0001). Following transfection of SNpc neurons with pAAV-hSyn-hM3D(Gq)-mCherry, chemogenetic activation of nigro-vagal nerve terminals by brainstem application of CNO increased proximal colon motility (157±24.5% of baseline; n=3; unpaired t test; p=0.0399). The increase in colon motility following SNpc neuronal activation was abolished by brainstem pretreatment with the dopaminergic DA1-like antagonist SCH23390 (n=4; one-way ANOVA, p=0.9762 vs baseline; p=0.0159 vs NMDA alone) as well as by acute subdiaphragmatic vagotomy (94±47.9% of baseline; n=3; One-way ANOVA, p=0.9816 vs baseline and p=0.0105 vs NMDA alone). In contrast to the excitatory effects observed upon activation of brainstem D1R following SNpc stimulation, DMV microinjection of DA decreased both the tone (-81±27.3mg, n=7) and motility (49±21.6% of baseline; n=7; paired t test: p=0.0004) of the proximal colon. These inhibitory DA effects were attenuated by application of the DA2-like antagonist L741646 (tone -100±58.9mg vs 99±100.1mg; n=4; paired t test: t3=2.567, p=0.0414 and motility 63±15% vs 144±38% of baseline; n=5; one-way ANOVA, p=0462 in the absence and presence of L741646).These data suggest that a monosynaptic nigro-vagal pathway activates brainstem D1 receptors to increase proximal colon tone and motility in a vagally-dependent manner. This study provides the anatomical and mechanistic basis to explain how loss of SNpc neurons may lead to gastrointestinal dysfunction, including constipation, observed in patients with Parkinson’s Disease. no disclose 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.
Neuronostatin accts as a counterregulatory factor to protect against hypoglycemia
Authors: Pate Alicia , Grote Stephen , Yosten Gina 
Published: May 2023

Neuronostatin (NST) is a 13-amino acid hormone derived from the somatostatin (SST) preprohormone that exerts metabolic and cardiovascular actions in many tissue types. In transformed alpha cell lines and isolated rat islets neuronostatin enhanced low glucose-stimulated proglucagon transcription and glucagon secretion1. Additionally, neuronostatin inhibited high glucose-stimulated insulin secretion from isolated rat islets, which was mirrored in vivo in rats subjected to an intra-arterial glucose tolerance test. Rats that received a bolus injection of neuronostatin followed by infusion glucose exhibited delayed glucose disposal and impaired insulin release, causing an increased peak blood glucose1. We, therefore hypothesized the ability of neuronostatin to act as a counterregularoty factor to protect against hypoglycemia. We found that Neuronostatin administered prior to an insulin tolerance test significantly reduced hypoglycemia compared to the saline control. In addition, we found that administration of exogenous Insulin significantly reduced Neuronostatin plasma levels. These data suggest Neuronostatin may act as a counterregulatory factor in adult, male rats to prevent hypoglycemia. However, after menopause or OVX, a precipitous decline in insulin sensitivity parallels an increase in fat mass, suggesting estrogens at physiological concentrations may maintain insulin action and glucose tolerance. We therefore investigated the neuronostatin-induced blood glucose changes in conscious, cycling females. We found blood glucose levels following neuronostatin administration decreased on diestrus, when both estrogen and progesterone levels are low, but not on proestrus or estrus. From these data we conclude that the metabolic actions of Neuronostatin are modulated by sex hormone status. Further studies are required to determine the contributions of chromosomal sex and individual sex hormones to these metabolic effects of Neuronostatin.1. Salvatori AS, Elrick MM, Samson WK, Corbett JA, Yosten GL. Neuronostatin inhibits glucose-stimulated insulin secretion via direct action on the pancreatic alpha-cell. Am J Physiol Endocrinol Metab. 2014;306:E1257–E1263. Saint Louis University Internal Funds 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.
Blunted sympathetic transduction to blood pressure in females with relapsing-remitting multiple sclerosis
Authors: Trotter Claire , Young Benjamin , Jarrard Caitlin , Smith Scott , Fadel Paul , Huang Mu , Davis Scott 
Published: May 2023

Approximately 1 million people in the United States are living with multiple sclerosis (MS) with nearly 75% of those being female. MS is a progressive demyelinating neurological disease of the central nervous system associated with a high prevalence of orthostatic hypotension. Our laboratory has previously shown that individuals with MS have a reduced ability to increase mean arterial pressure during simulated hypotension which was attributed to a blunted vascular response. The purpose of this project was to investigate how spontaneous bursts of muscle sympathetic nerve activity (MSNA) induce end-organ response(s) and ultimately evoke a change in blood pressure (BP) on a heartbeat-to-heartbeat basis in females with MS, a process known as sympathetic transduction to BP. We tested the hypothesis that females with MS have reduced resting sympathetic transduction to BP compared to sex-, height-, weight-, age- and race-matched healthy controls. Beat-to-beat BP (Finometer) and MSNA (peroneal microneurography) were continuously recorded during 10 minutes of quiet supine rest in 9 females with relapsing-remitting MS (age: 39.6 ± 3.3 years; Expanded Disability Status Scale < 6.0) and 10 healthy female controls (age: 35.4 ± 2.1 years). Total vascular conductance (TVC) was estimated using modelflow. Sympathetic transduction was determined by identifying the peak change in diastolic BP and the nadir reduction of TVC over 10 cardiac cycles following spontaneous MSNA bursts using signal averaging. No differences were detected in resting mean arterial pressure (MS: 88 ± 3 mmHg; controls: 85 ± 2; P = 0.42) or MSNA burst frequency (MS: 26 ± 3 bursts/min; controls: 19 ± 3 bursts/min; P = 0.11) between groups. Peak increases in diastolic BP following MSNA bursts were lower in females with MS (1.2 ± 0.2 mmHg) compared to controls (2.5 ± 0.6 mmHg; P = 0.039). Whereas no differences were observed in nadir reductions in TVC (MS: -1.7 ± 0.5 ml/min/mmHg; controls: -3.0 ± 0.8 ml/min/mmHg; P = 0.11). These preliminary data suggest that sympathetic transduction to BP is blunted in females with MS. Reduced sympathetic transduction to BP may contribute to the high occurrence of orthostatic hypotension in this clinical population. Further investigation is warranted to help better understand the potential mechanism(s) underlying lower sympathetic transduction in females with MS. This work was supported by American Heart Association Predoctoral Fellowship (Award #915655, Trotter) and American College of Sports Medicine Doctoral Research Grant (Award # 19-01141, Trotter) 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.
The SGLT2 inhibitor, empagliflozin reduces early progressive proteinuria in obese SS rats
Authors: Ekperikpe Ubong , Daniels Jacori , Mandal Sautan , Cooper Jonita , Johnson Tyler , Safir Sarah , Cornelius Denise , Williams Jan 
Published: May 2023

Childhood/prepubertal obesity (PPO) is a world-wide epidemic and is considered a risk factor for renal injury. Therefore, there is a need to control this trend to decrease the future risk of chronic kidney disease. Recently, we reported that the SSLepRmutant rat is a novel model to study the mechanisms of renal injury associated with PPO. The SSLepRmutant rat develops progressive renal injury in the absence of hyperglycemia before puberty. SGLT2 inhibitors have been demonstrated to exert renoprotective effects independent of lowering blood glucose. Therefore, the objective of this study was to determine the effects of SGLT2 blockade with empagliflozin on the early progression of proteinuria in SSLepRmutant rats, during PPO. Four-week-old SS and SSLepRmutant rats (n = 5/group) were either treated with vehicle (diet) or empagliflozin (30 mg/kg/day, orally) for four weeks. While the SSLepRmutant rats had significantly higher body weights vs SS rats, there were no detectable differences in body weight or blood glucose levels in response to empagliflozin treatment in SSLepRmutant rats. We observed a significant increase in plasma insulin in control SSLepRmutant rats vs SS rats (7±1 vs 1±0.3 ng/mL, respectively, p<0.05), and treatment with empagliflozin did not have any effect on plasma insulin in SSLepRmutant rats (8±2 ng/mL). At baseline, we did not observe any significant difference in urine flow rate between control SSLepRmutant vs SS rats. After two weeks of treatment, while there was no observed difference in urine flow rate between SSLepRmutant and SS rats (17±3 ml/day vs 18±2 ml/day, respectively), empagliflozin significantly increased urine flow rate in SSLepRmutant rats (29±4 ml/day, p<0.05), but not in SS rats (17±3 ml/day). At baseline, we observed a difference in proteinuria between control SSLepRmutant vs SS rats (68±11 vs 6±3 mg/day, respectively, p<0.05), which remained elevated over the course of the study (471±75 vs 32±5 mg/day, respectively, p<0.05). Treatment with empagliflozin significantly decreased proteinuria in SSLepRmutant rats (223±52 mg/day, p<0.05) without affecting SS rats (27±8 mg/day). At the end of the study, we observed a significant increase in GFR in control SSLepRmutant rats vs SS rats (2.4±0.6 vs 0.5 mL/min/gkwt, respectively, p<0.05). Treatment with empagliflozin only significantly reduced GFR in SSLepRmutant rats (0.9±0.2 mL/min/gkwt, p<0.05). In conclusion, these data suggest that empagliflozin attenuates renal hyperfiltration and confers renoprotective effects during the early progression of renal disease associated with PPO. DK109133 and HL151407 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.