bluuebunny/crossref_metadata_2025_split huggingface dataset:
Arrdc4 Regulates Insulin‐Stimulated Glucose Metabolism
Authors: Dagdeviren Sezin , Shah Anu , Okawa Marinna , Melnik Veronika Y. , Sarikhani Mohsen , Foot Natalie , Kumar Sharad , Lee Richard T. 
Published: April 2020

The molecular mechanisms that control glucose uptake into the cells are not yet completely defined. The Arrestin superfamily of proteins controls the inactivation, degradation and signaling of trans‐membrane receptors. Several members of the family, including Arrestin domain containing 3 and TXNIP, are now known to have important roles in metabolism. Arrestin domain containing protein 4 (ARRDC4) is a less‐investigated member of the ancient alpha‐arrestin family. Here, we show that ARRDC4 controls insulin‐stimulated glucose metabolism in vivo and in vitro. Both ARRDC4 and TXNIP suppressed insulin‐stimulated glucose uptake in differentiated adipocytes (Fig.
). In 8‐week old male C57Bl6 wildtype mice and mice with systemic deletion of the ARRDC4 gene (n=5–7/group) subjected to insulin tolerance tests (0.75U/kg), we found that mice with deletion of ARRDC4 were significantly more insulin sensitive compared to wildtype mice (Fig
). We also found that deletion of ARRDC4 in mice led to increased insulin‐stimulated Akt phosphorylation in adipose tissues (Fig
). Furthermore, in vitro and in mice, the expression of ARRDC4 is suppressed by insulin (Fig
). These data identify ARRDC4 as a regulator of mammalian insulin‐stimulated glucose metabolism.Support or Funding InformationSupported by NIH/NIDDK to R.T.L 1R01DK107396(A) Insulin‐stimulated H3 deoxy‐glucose uptake in differentiated 3T3‐L1 mature adipocytes that were transfected with either empty, ARRDC4 or TXNIP plasmid (n=6) (B) Insulin tolerance test (0.75U/kg) of 8‐week old ARRDC4 KO and WT mice (n=5–7) (C) Insulin‐stimulated Akt phosphorylation in adipose tissues of ARRDC4 KO and WT mice. ARRDC4 mRNA expression in the insulin‐stimulated HEPG2 cells (D) or livers of wildtype mice (E) (n=4) *p<0.05 **p<0.01.Figure 1
SPARC: Method for Overcoming Temporal Dispersion in Unmyelinated Nerves for Imaging C Fibres with Electrical Impedance Tomography (EIT)
Authors: Tarotin Ilya , Mastitskaya Svetlana , Hannan Sana , Ravagli Enrico , Aristovich Kirill , Holder David 
Published: April 2020

Fast neural EIT is a novel technique that enables imaging of evoked myelinated fibre activity in fascicles in rat sciatic nerve in vivo. However, imaging unmyelinated fibres is challenging due to temporal dispersion of the neural activity, caused by variability in fibre conduction velocities. This reduces the signal to below noise several centimetres from onset. The purpose of this work was to develop a method to overcome dispersion and allow EIT recordings of phasic activity at any distance from onset along the nerve.MethodsCompound impedance changes (dZ) were simulated using an electrically stimulated CAPs in 1D FEM model of a C fibre
[1], with statistical analysis for 5000 fibres with conduction velocities 0.6±0.07 m/s (mean±SD)
[2]. This enabled simulation of dZ up to 20 cm from the stimulus with stimulus trains of 5/10/20/50 Hz lasting 0.25–8 s with 3 s intervals between trains (Fig.
1a). The total duration of each simulation was 100 s.dZ was simulated 1) By coherent averaging of responses of supramaximal activity of single spikes
[3] with demodulation bandwidth of 50–300 Hz and 2) By bandpass filtering of entire evoked spike trains with bandwidths of 0.25–5 Hz which allowed significant reduction of the noise without the need for coherent spike averaging.Random gaussian noise (0.015 μV RMS) was added to the signal to simulate realistic recording conditions. The SNR in the utilised approaches was computed for all tested stimulation and recording paradigms and compared.ResultsWhile coherent spike averaging was superior at short distances, its SNR fell exponentially with the distance from the onset (Fig.
1b, solid lines). The SNR with the compound demodulation was more consistent across distances (~2 at the optimal stimulation frequency of 20 Hz, Fig.
1b, dashed lines) allowing recording at ≥ 20 cm from stimulation. The estimated minimal averaging time required to obtain an SNR of 4 at 20 cm from the stimulus was equal to approximately 30 minutes at 20 Hz.Conclusion and future workThe developed stimulation and signal processing paradigm demonstrated the feasibility of dZ recording at long distances from the stimulus. Future work is to validate it on the ex vivo crustacean leg nerve model and subsequently an in vivo mammalian model with the final objective of imaging C fibres in the vagus nerve in humans. If successful, this technique will be applied for improvement of the emerging field of bioelectronic medicines
[4].Support or Funding InformationThe work was supported by NIH SPARC grant no: 3OT2OD026545‐01S2.(a) Example of AP and dZ responses of the C fibre subjected to repetitive 50 Hz stimuli; (b) SNR computed for the single and compound recording paradigms.Figure 1
The Role of Coenzyme A Degradation in the Regulation of Peroxisomal Metabolism
Authors: Vickers Schuyler D. , Shumar Stephanie A. , Leonardi Roberta 
Published: April 2020

Coenzyme A (CoA) is an essential metabolic cofactor that activates fatty acids and other organic acids as CoA thioesters for a multitude of metabolic pathways in different subcellular compartments. For example, CoA is utilized in the bile acid synthesis pathway and for shortening of very long chain fatty acids in the peroxisomes. The regulation of CoA levels is essential to maintain metabolic flexibility in response to changes in nutritional status and energy demands. Balance between CoA synthesis and degradation is responsible for the regulation of CoA. While CoA synthesis is controlled at the pantothenate kinase step, the intracellular degradation of CoA is controlled by Nudix hydrolases. Nudt7 is a hepatic, peroxisomal Nudix hydrolase that specifically hydrolyzes CoA species into 3’,5’‐ADP and (acyl)phosphopantetheine. Nudt7 displays a broad substrate specificity; it is active against free CoA, short‐ and medium‐chain acyl‐CoAs, including acetyl‐CoA, and the acyl‐CoA derivatives of bile acids. Nudt7 expression and activity are regulated by nutritional state, as they both decrease upon fasting. Overexpression of Nudt7 in the liver was recently found to decrease the levels of a variety of short‐chain acyl‐CoAs and choloyl‐CoA in the liver, and to decrease the rate of peroxisomal β‐oxidation. To gain further insight into the role of Nudt7 in vivo, Nudt7−/− mice were generated and their lipid metabolism assessed. Deletion of Nudt7 caused a small but significant increase in total hepatic CoA levels in the fasted state. In particular, higher concentrations of malonyl‐and acetyl‐CoA were observed. Furthermore, livers from Nudt7−/− males contained higher levels of short‐chain fatty acids and short‐chain acylcarnitines, which, combined, suggest an increase in fatty acid oxidation. In the fed state, female Nudt7−/− mice exhibited a higher concentration of selected bile acids in the intestine, while feeding of a high fat high/cholesterol diet resulted in higher bile acid levels in the liver. This increase in bile acids occurred without changes in the expression of genes involved in bile acid synthesis or transport and without a correspondent increase in the concentration of bile acid precursors 7α‐hydroxycholesterol and 7α‐hydroxycholestenone. These results suggest that higher CoA levels in the peroxisomes may mediate an increase in flux through the bile acid biosynthetic pathway by activating of the last, peroxisomal steps in the pathway.Overall, analysis of lipid metabolism following manipulation of Nudt7 expression in mouse liver indicates that this enzyme contributes to the regulation of peroxisomal fatty acids and bile acid metabolism.Support or Funding InformationThis work was supported by West Virginia University’s School of Medicine startup foundation funding and NIH grant GM119528.
A Coupled Electromechanical Myocyte Model to Assess the Effects of 2‐deoxy‐ATP on Contractile Function in the Heart
Authors: Teitgen Abigail , McCabe Kimberly , Hock Marcus , Regnier Michael , McCulloch Andrew 
Published: April 2020

IntroductionHeart failure (HF) remains a significant cause of morbidity, mortality, and medical costs. HF is characterized by reduced contractile function and inability of the heart to pump sufficient blood to meet the body’s demands. Existing treatments for HF do not permanently restore cardiac function and can lead to side effects such as impaired ventricular relaxation. 2‐deoxy‐ATP (dATP), a novel heart failure therapeutic, has been shown to increase contractile function while enhancing relaxation
[1]. Previous studies have shown that dATP increases the rate of crossbridge cycling
[2]. It has also been shown that dATP acts on the sarcoplasmic reticulum ATPase (SERCA), the pump responsible for removing calcium (Ca2+) from the cytosol, which could explain the enhanced relaxation kinetics seen experimentally
[3]. However, the mechanism of dATP is still not fully understood. Further, it is not clear whether the increased rate of crossbridge cycling with dATP treatment could aggravate energy starvation in HF.MethodsTo assess the full mechanism of dATP at the cellular level, we utilized a myocyte model containing several ion channels, including SERCA
[4]. We coupled this model to a mitochondria model to investigate whether dATP treatment aggravates energy starvation by tracking ATP, ADP, Pi, and oxygen concentrations over time
[5]. We also coupled the myocyte model to a previously developed 5 state Markov model of crossbridge cycling, which captures regulation of contraction via Ca2+ binding to troponin
[2]. The crossbridge cycling model was modified to capture the effects of sarcomere length on Ca2+ sensitivity. dATP treatment was simulated by adjusting the ATP and Ca2+ binding rates in the SERCA model and the rate of crossbridge cycling in the sarcomere model based on previous studies
[2,
3].Results and ConclusionsWe found that the combined effects of dATP on both SERCA and the sarcomere within the coupled myocyte model could explain the increase in fractional shortening and time to 50% and 90% relaxation of the Ca2+ transient seen experimentally more accurately than either model alone. Additionally, we found no evidence that dATP aggravates energy starvation, affirming dATP as a promising therapeutic for HF.Support or Funding InformationNIH HLT32 TG
Evaluation of a Putative PPAR Modulator
Authors: Skeels Amy , Cumbay Medhane , Strom David , LaFontaine Michael 
Published: April 2020

BackgroundPeroxisome Proliferative‐Activated Receptors (PPAR) are part of a superfamily of receptors. Of the PPARs, three forms are most prevalent, PPAR‐a, PPAR‐b/d and PPAR‐g that bind FA & FA‐derivatives to their receptor domains. Each PPAR consists of an AF‐1 domain, DNA‐binding domain, dimerization domain, and ligand‐binding domain. (1) When a lipid‐derived ligand binds to a PPAR, the PPAR heterodimerizes with a retinoid X receptor (2). This heterodimer will bind a co‐activator protein (3), which in turn activates a peroxisome proliferator response element (PPRE) (1,2). The PPRE is located in a promoter region of the target genes of a DNA sequence that will allow for trans‐activation or ‐repression of gene expression. (4.) Previous data has been collected regarding a drug compound called Compound 9, which was a dual agonist of PPARg and PPARd. The compound tested, benzyl derivative, called BMZ is a derivative of compound 9.ObjectivesTest novel compound, a demethylated derivative of a previously used compound, called BMZ, to determine its activation of PPAR receptors.MethodsTo test BMZ activation of PPAR receptors, HeLa cells were plated into 96 well plates and transfected with PPRE‐3x‐TK‐luciferase (520ng/l), Trans IT‐X2 transfection reagent, and serum reduced media. The cells were then treated with troglitazone, pioglitazone, and BMZ with the following concentration in separate wells in triplicate, 0.1mM, 0.3 mM, 1.0 mM, 3.0 mM, 10 mM, 30 mM. Triplicate wells were also treated with 10 mM of BMZ with 10 mM of troglitazone. Finally, a separate triplicate of Compound 9 was added. A luciferase assay was conducted 24 hours after application of drug in five, five minute intervals.ResultsThe results showed that there was some activation of PPAR receptors for the novel BMZ compound. Furthermore, when BMZ was added to troglitazone, there was an decreased activation of the receptors.Support or Funding InformationMarian University College of Osteopathic Medicine Internal GrantRelative Luminescence Units of various PPAR‐gamma agonistsFigure 1
Opioids Cause Vascular Remodeling via Changes in Cofilin‐ERK Signaling: Female Mice Present Higher Risk of Developing Morphine‐induced Cardiovascular Disease than Male Mice
Authors: Cheon Soyoung , Tomcho Jeremy C. , Bearss Nicole R. , Joe Bina , McCarthy Cameron G. , Wenceslau Camilla F. 
Published: April 2020

According to the most recent CDC Annual Surveillance Report of Drug Related Risks and Outcomes, more than 47,600 people died from an opioid overdose in 2017 in the United States. The magnitude of the national crisis raises questions on intersecting points between opioid abuse and the main systems of the human body. Recent statistical analyses have shown that chronic use of prescription or illicit opioids leads to an increased risk of a cardiovascular event, which was higher among women than men. We hypothesized that chronic exposure to exogenous opioids causes sex‐specific vascular remodeling via changes in actin polymerization, leading to an increased risk of cardiovascular disease. In a preliminary study to test our hypothesis, we observed that treatment with the exogenous opioid morphine (≥ 24 hours) induced vascular smooth muscle cell proliferation. Acknowledging the emerging roles of cofilins and extracellular signal‐regulated kinases (ERK) in the regulation of cell proliferation by mediating actin dynamics, we investigated the effects of morphine (MOR) on the intracellular levels of both proteins in vasculature. Mesenteric resistance arteries (MRA) from 10 week old wild type C57BL/6NTac male and female mice were extracted (n=4). The MRA of each animal were isolated and divided equally into control and treatment groups. The control and treated samples were incubated in DMEM with 1% penicillin‐streptomycin at 37°C for 24 hours in the absence or presence of MOR (1μM) respectively. We observed that MOR increased phosphorylated/inactivated cofilin 1.6 fold [arbitrary units (AU), control: 0.59 ± 0.14 vs MOR: 0.95 ± 0.10*, *p<0.05] and increased phosphorylated/activated ERK 1.8 fold (AU, control: 0.51 ± 0.11 vs MOR: 0.90 ± 0.13*, *p<0.05) in the MRA from female mice. On the other hand, MOR decreased phosphorylated ERK 1.5 fold (AU, control: 0.91 ± 0.08 vs MOR: 0.59 ± 0.11*, *p<0.05) but had no effect on the levels of phosphorylated cofilin (p>0.05) in the MRA from male mice. Our data suggest that exogenous opioids change actin dynamics in arteries from both male and female mice. Further, this study is the first to demonstrate that prolonged exposure to morphine may increase cardiovascular risk in females when compared to males.Support or Funding InformationThis work was supported by National Institutes of Health (NIH) (NIH: R00GM118885).Levels of phosphorylated cofilin (left) and ERK (right) in MRA from male and female mice after 24 hours of treatment with morphine (MOR, 1μM) or vehicle.Figure 1
Mitochondria Influence NMDA Receptor‐mediated Currents in Hypothalamic Magnocellular Neurons: Altered Mechanisms during Heart Failure
Authors: Ferreira-Neto Hildebrando Candido , Stern Javier 
Published: April 2020

Hypothalamic magnocellular neurosecretory neurons (MNNs) located in the supraoptic (SON) and paraventricular nuclei (PVN) play a critical role in the pathophysiology of heart failure (HF). Mitochondria (MITO) plays an important role in the regulation of intracellular Ca2+ dynamics, and several studies observed that morphological and functional MITO changes contribute to the development and maintenance of various brain diseases. We recently demonstrated that NMDA receptors activation triggers a Ca2+−dependent stimulation of SK channel in MNNs from Sham rats, and that this coupling acts as a negative feedback mechanism restraining the magnitude of the NMDA receptor‐mediated current (INMDAR) and its excitatory effects. Importantly, we found that the NMDA‐SK channel coupling is blunted in MNNs from HF rats. Still, whether MITO regulation of intracellular Ca2+ dynamics influence INMDAR and whether this effect is altered during HF is unknown. To address this question, we obtained whole‐cell patch clamp recordings from MNNs (holding potential: −50 mV) in slices from Sham and HF rats. We found that focal application of NMDA (50 μM, 300 ms) evoked an INMDAR whose magnitude was similar in Sham and HF rats (p>0.05), as previously reported. Application of CCCP (10 μM, 5 s), a mitochondrial uncoupler, significantly increased the evoked INMDAR in MNNs from Sham rats (p<0.05), but had no effect in MNNs from HF rats (p>0.05). Intracellular dialysis of MNNs with the Ca2+ chelator BAPTA (10 mM) significantly augmented INMDAR in MNNs from Sham rats compared to the control condition (p<0.05), and occluded the CCCP‐induced INMDAR increase. Taken together, our data supports that mitochondria regulate, in a Ca2+‐dependent manner, the magnitude of INMDAR in MNNs from Sham rats, a phenomenon that is blunted during HF.Support or Funding InformationR01HL090948
Deletion of the mechanistic‐target‐of‐rapamycin (mTOR) from collecting duct principal associated with increased ubiquitinylation of epithelial sodium channel (ENaC)
Authors: Chen Bruce , Fluitt Maurice B. , Shivapurkar Narayan , Brown Aaron , Ecelbarger Carolyn Mary 
Published: April 2020

The mechanistic target of rapamycin (mTOR), a serine‐threonine‐specific kinase, is a cellular energy sensor, integrating growth factor and nutrient signaling. In the renal collecting duct (CD) or in related cell cultures, mTOR has been demonstrated to upregulate activity of the epithelial sodium channel (ENaC). Our aim was to determine the impact of CD‐principal‐cell‐select mTOR deletion on the adaptations to changes in dietary sodium and elucidate ENaC regulation. Male and female CD‐PC mTOR KO mice and wild‐type (WT) littermates were generated by Cre‐lox recombination using aquaporin‐2 (AQP2) promoter to drive Cre‐recombinase. KO mice had 20–40% reduced protein levels of all three subunits of ENaC under low‐ (0.5% Na+, LSD) or normal‐NaCl (< 0.02% Na+, NSD). Switching from NSD to LSD resulted in transiently increased urine sodium losses (day 1) in the KO, with adaptation by day 2. Likewise, KO were significantly impaired (20% less Na+ excretion) on day 1 in transitioning from NSD to high‐NaCl (4%) diet. Under NSD, an in vivo acute test of benzamil‐sensitivity supported reduced (~30%) ENaC activity in the KO; however, 24‐hour urine collection after dietary BNZ (5 mg kg·bw) showed increased Na+ losses in the KO. No genotype differences in blood pressure (BP, tail cuff) were observed under NSD; however, LSD surprisingly increased BP in WT, but not KO. Apical targeting of ENaC subunits with LSD appeared intact (after 7‐days of LSD). To interrogate the mechanisms for reduced ENaC subunit protein levels, an ubiquitination ELISA assay was conducted on cortex homogenates probing for ubiquitinated a‐ENaC. KO mice demonstrated 50–100% higher density for immunoprecipitated ubiquitin probed for a‐ENaC, as compared to WT mice in both males and females. Our data support a role for mTOR in ENaC activity and sodium homeostasis potentially via regulation of ENaC subunit turnover.Support or Funding InformationBGRO Georgetown University and Marriott Cardiovascular Foundation (CE); American Diabetes Association (MF); Department of Biochemistry, GU (AB)ENaC was localized to the apical membrane in both WT and KO mice with low‐NaCl feeding.Figure 1Increased ubiquitination of alpha‐ENaC in CD‐principal cell targeted mTOR KO miceFigure 2
Pontine Parabrachial Nucleus (PBN) Neuron Subtypes Involved With the Control of Breathing Frequency
Authors: Zuperku Edward J. , Hopp Francis A. , Stuth Eckehard A. , Stucke Astrid G. 
Published: April 2020

A subregion within the medial PBN plays a key role in the control of expiratory duration (TE) and breathing frequency (fB)
1. Drug‐induced increases in neuronal activity decrease TE, while depression of these neurons increases TE. Activity from these neurons is relayed with short latencies to neurons in the preBötzinger/Bötzinger region
2. This study analyzed the relationship between charateristics of the discharge frequency (Fn) patterns of I, E, phase spanning and non‐respiratory modulated (NRM) PBN neurons and changes in fB induced by local application of neural transmitter agonist and antagonist. Multichannel neuronal recording with highly localized microinjections into the PBN were performed in decerebrate, vagotomized dogs during isocapnic hyperoxia. The phrenic neurogram was used to assess fB responses and identify neuronal discharge patterns. Plots of fB vs. neuronal Fn during induced fB responses produced by microinjections of AMPA and the GABA‐A receptor antagonist bicuculline (BIC) were linear with high correlation values (r > 0.75). Furthermore, it appears that neurons with little or no respiratory modulation appear to be more highly correlated with fB than neurons with strong phasic patterns, suggesting that these neurons may be responsible for the pontine control of fB.Support or Funding InformationSupported by Department of Veterans Affairs grant 2 I01BX000721‐08 (Zuperku) & R01GM112960‐01A1 (Stucke)Example of breathing frequency response (BPM) to microinjected AMPA (green) in PBN and corresponding neuronal responses (red) for 2 neurons (panel A and panel B). Lower: Plots of BPM vs discharge frequency (Fn = Fmax) for two simultaneously recorded neurons, phasic‐I (A) and NRM (B) with corresponding slope and r‐squared values. Top: Cycle‐Triggered Histograms (CTHs)Figure 1