bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dietary Nitrate and Skeletal Muscle Recovery after Injury in Young and Old Mice
Authors: Hahn Dongwoo , Patel Ravi , Kelley Rachel C , Coblentz Philip D , Ferreira Leonardo F 
Published: November 2023

Nitric oxide availability has been shown to modulate skeletal muscle hypertrophy and regeneration post‐injury. Aging decreases nitric oxide availability and delays skeletal muscle recovery from injury. Dietary nitrate increases nitric oxide availability in skeletal muscle vessels and fibers. However, it is unclear whether dietary nitrate can accelerate aged skeletal muscle regeneration post‐injury. Therefore, our goal was to investigate the effect of dietary nitrate on skeletal muscle recovery from injury in aging. Young (n=36, 6 months old) and old (n=20, 24 months old) mice received sodium nitrate (NaNO3, 1mM) in drinking water or vehicle (deionized H2O) ad libitum for a total of 14 days. Seven days after the start of treatment, we injected cardiotoxin (CTX, 10 μM) into the tibialis anterior (TA) and extensor digitorum longus (EDL) from one limb, and saline into muscles of the contralateral limb. Seven days post‐injection, we collected the TA and EDL for measurements of muscle force, morphology, protein and mRNA. CTX decreased TA and EDL weights by ~30% each (p < 0.05), and the effects were independent of age or treatment. CTX decreased EDL maximal tetanic absolute (mN) and specific force (N/cm2) by 65% and 50% (P < 0.05 vs. non‐injected controls), respectively, and the effects were independent of age or treatment. CTX increased protein abundance of myogenin in the TA, an effect that was independent of age or treatment. Dietary NaNO3 decreased protein levels of embryonic myosin heavy chain (eMHC) in saline‐injected TA of old animals, whereas eMHC protein abundance increased after CTX injection. Protein levels of eMHC in CTX‐injected TA of animals receiving NaNO3 were similar to those from CTX‐ and saline‐injected muscles of old mice drinking vehicle. Overall, our data heretofore suggest that dietary NaNO3 did not accelerate the recovery of skeletal muscle force and weight, or markers of myogenesis in young and old animals. An interesting observation was that dietary NaNO3 decreased the levels of eMHC in saline‐injected muscle from old animals.Support or Funding InformationNIA R03 AG040400‐02
The Effects of Low‐Intensity Exercise during Bed Rest in Healthy Older Adults
Authors: Galvan Fego , Arentson‐Lantz Emily , Nagamma Sneha , Deer Rachel R. , Fry Christopher S. , Wacher Adam , Paddon‐Jones Douglas 
Published: November 2023

Aging results in the involuntary loss of muscle mass and strength. These rates of decline are exacerbated with hospitalization, illness, and injury (i.e., catabolic stressors). Acutely ill, hospitalized adults have significantly reduced daily activity (~740 steps/day) compared to their healthy counterparts (~6250 steps/day). While intense exercise is clearly not practical for older, hospitalized individuals, low‐intensity exercise may be a more practical alternative. 60 minutes of daily longitudinal loading (1G artificial gravity/centrifugation) has been shown to maintain muscle protein synthesis during bed rest in a young adult population. Thus, we hypothesized that low‐intensity exercise (2,000 steps/day) would mitigate the loss of muscle mass and function during 7‐days of bed rest in healthy older adults.We employed a 7‐day bed rest protocol as a model of the physical inactivity associated with hospitalization. Dietary intake and daily steps were strictly controlled. Volunteers were randomized into two experimental groups: bed rest alone (CON: N=10, 68±5 y) or bed rest + 2,000 daily steps (STEP: N=7, 68±6 y). Isometric strength, leg lean mass (LLM) and blood glucose area under the curve (AUC) were assessed at baseline and after 7‐days of bed rest. Changes in isokinetic extension (60°/s) (CON: −13.3±3.3 N·m vs STEP: −14.4±3.8 N·m), LLM (CON: −932.3±181.8 g vs STEP: −700.4±149.2 g), and blood glucose AUC (CON: 456.4±1016.5 mg/dl/120 min vs STEP: −901.4±986.4 mg/dl/120 min) were similar between groups.Data from this ongoing clinical trial suggests that a single bout of 2,000 steps/day is not sufficient to counter the catabolic effects of 7‐days bed rest in healthy older adults. Future exploration of the effects of a greater number of steps/day, the combined effects of nutritional support plus exercise or distributing activity across the day may be needed to have clinically translatable benefits.Support or Funding InformationSupported by RO1 NR012973, P30 AG024832.
Aberrant Light‐Induced Depression is Associated with Decreased Adult Hippocampal Neurogenesis in Mice
Authors: Massman Logan Joseph , Engeland William C , Kofuji Paulo 
Published: November 2023

In today's world of constant activity, people are frequently exposed to light outside of the natural daytime hours. This leads to a disruption in the endogenous circadian rhythm resulting in various mood disorders in humans (Bedrosian and Nelson 2013). In mice, it has been shown that aberrant light is sufficient to induce a depressive‐like phenotype; however, there is no clear explanation of the neurological basis for this phenomenon except light input is transmitted by intrinsically photosensitive retinal ganglion cells (Legates et al 2012). In other mouse models of depression, adult hippocampal neurogenesis (AHN) has been shown to be decreased (Mahar et al 2014). This study tested whether aberrant light‐induced depression was associated with decreased AHN in mice. Adult male C57B/6 mice were housed in standard light conditions (12:12 hours (T24) LD) or aberrant light conditions (3.5:3.5 hours (T7) LD) for at least three weeks prior to testing. Mice were assayed for a depressive‐like phenotype using a two‐bottle sucrose preference test over four days. Mice exposed to T7 LD showed significant reductions in sucrose preference compared to mice on T24 LD. Immunohistochemical fluorescent labeling for the cell proliferation marker Ki‐67 was then used to quantify AHN in the dentate gyrus. Mice under T7 LD had significant reduction of AHN compared to mice on T24 LD. These parallel observations of decreased sucrose preference and decreased AHN resulting from chronic exposure to aberrant light (T7 LD) suggest that AHN may provide the neurological basis for aberrant light‐induced depression.Support or Funding InformationAPS Undergraduate Summer Research Fellowship and NIH RO3NS094419
Copeptin: More than Just a Surrogate Biomarker
Authors: Haddock Christopher J. , Wille Hannah M. , Yosten Gina L.C. , Samson Willis K. 
Published: November 2023

Copeptin is a 39 amino acid peptide derived from the vasopressin preprohormone. The function of vasopression is well characterized; however, the receptor and physiological function of copeptin remain unknown. These peptides are secreted at a 1:1 ratio, indicating that the actions of vasopression could “mask” the effects of copeptin. Thus, the physiologic effects of copeptin have been difficult to ascertain. Currently, copeptin is used as a surrogate biomarker for vasopression secretion due to the short half‐life of and difficulty measuring vasopression, but the biological activity of copeptin has not been confirmed. To evaluate the potential biological effects of copeptin, we exposed three cell types (HEK293, KATOIII, and ARPE19) to increasing concentrations of copeptin. Using real time quantitative PCR we have discovered that incubation with 100nM copeptin leads to increases in mRNA expression of the early transcriptional activation marker c‐FOS in all three cell types. Transcriptional activation indicates that copeptin is working through a receptor, and because the effects of vasopressin are mediated through G protein‐coupled receptors (GPCRs) V1, V2, and V3, we hypothesize that copeptin also signals through a GPCR. We are testing this hypothesis using a “deductive ligand‐receptor matching strategy” developed in our lab. Candidates for a potential receptor fall into a class of GPCRs with no known ligand, Orphan GPCRs. To narrow the pool of candidate receptors for copeptin, we have compared expression profiles of all orphan GPCRs in the copeptin‐responsive cell lines. This strategy generated a short list of orphan GPCRs expressed by all three cell types. One of the candidate receptors expressed in all responding cell types is likely responsible for mediating the transcriptional effects of copeptin. We are using knockdown/rescue experiments to determine which receptor copeptin is signaling through. We also are developing an animal model to determine the physiologic effects of copeptin, leading to a better understanding of the function of this peptide.Support or Funding InformationNIH HL121456
Determining the Role of CEBP/α in Functional β‐cell Mass
Authors: Kener Kyle B , Ray Jason D. , Ballard Matthew , Utsch Will , Tessem Jeffery Sivert 
Published: November 2023

Type 1 and type 2 diabetes both result in decreased functional β‐cell mass. Increasing functional β‐cell mass could be used as a cure for diabetes, either through the ex vivo expansion of β‐cells for transplantation or through in vivo expansion of endogenous β‐cells. We have shown that Nkx6.1 is necessary and sufficient to increase functional β‐cell mass by increasing proliferation, enhancing β‐cell function, and improving β‐cell survival. Furthermore, we have shown that c‐Fos is a critical early‐activated Nkx6.1 target gene that is essential to implement this molecular pathway. Here we demonstrate that CEBP/α is necessary for Nkx6.1 mediated upregulation of c‐Fos. We show that Nkx6.1 induces expression of CEBP/α, and that CEBP/α induces expression of c‐Fos. We show that CEBP/α is sufficient to induce β‐cell proliferation. We show that overexpression of CEBP/α protects β‐cells from apoptotic stimuli. We demonstrate the effect of CEBP/α overexpression on glucose stimulated insulin secretion. These data support the hypothesis that CEBP/α is part of the Nkx6.1 pathway for maintaining and increasing functional β‐cell mass and suggest that CEBP/α could be used as a potential target for enhancing functional β‐cell mass.Support or Funding InformationBYU MEG Grant to JST, BYU ORCA Grant to JDR and KBK
Free Fatty Acid Receptor 3 Plays a Role in High Fat Diet Induced β Cell Dysfunction and β Cell Stress
Authors: Priyadarshini Medha , Ludvik Anton E , Cole Connor , Newman Marsha , Layden Brian T 
Published: November 2023

A role of the gut microbiota in the development of both type 1 and type 2 diabetes has been suggested. The free fatty acid receptor 3 (FFA3) is considered to be a nutrient sensor that may be mediating the gut microbiota actions via the gut microbial metabolites, short chain fatty acids. As this receptor is expressed in β cells, a suggested metabolic interface may be occurring between β cells and the gut microbiota. We have previously shown that FFA3 inhibits β cell function in islets ex vivo. Exploring the physiological relevance of this observation in vivo, male mice with genetic knockout (KO) of FFA3 and their wildtype (WT) littermates were characterized with regard to glucose homeostasis. It was found that FFA3‐KO mice exhibit significantly higher insulin secretion and glucose infusion rates in hyperglycemic clamps consistent with enhanced insulin secretion by FFA3‐KO islets ex vivo. No differences were observed in energy expenditure, glycemic status and insulin sensitivity in FFA3‐KO and WT mice. With the exception of significantly enhanced insulin secretion in FFA3‐KO as compared to the WT mice upon intraperitoneal glucose challenge, no overt metabolic phenotype was observed under normal physiologic conditions. To investigate if FFA3 contributes to the β cell response to stress, two different models were utilized. First, under metabolic stress induced by high fat diet feeding, the WT mice developed impaired glucose tolerance as compared to the FFA3‐KO mice, owing mainly to enhanced insulin secretion with FFA3‐KO mice. Despite less insulin secretion (50–70% lower as compared to FFA3‐KO mice), WT mice had similar islet architecture and islet mass as FFA3‐KO mice. Surprisingly, challenge with single high dose of streptozotocin (STZ, agent inducing β cell damage), led to accelerated incidence of diabetes development in FFA3‐KO mice compared to the WT mice. Additionally, greater insulin deficiency and decreased β cell mass was observed in FFA3‐KO mice following STZ treatment, as compared to WT mice. Taken together, FFA3 mediates insulin secretion and the β cell response to high fat diet feeding without alteration in the islet mass. FFA3 also regulates the β cell responses to STZ treatment. Thus, these data demonstrate that FFA3 plays an important role in insulin secretion and β cell response to stressors.Support or Funding InformationSupport for the project has been from the Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, Career Development Grant No.1IK2BX001587‐01 (to B. T. Layden). M. Priyadarshini is supported by an American Heart Association postdoctoral fellowship (no. 15POST22410016).
Chronic Hypertension Switches Irritant‐Induced Pulmonary‐Cardiac Reflexes to Sympathoexcitation
Authors: Taylor‐Clark Tom , Hooper J Shane 
Published: November 2023

Inhalation of pollutants acutely increases morbidity and mortality in individuals with pre‐existing cardiovascular disease. In these individuals, pollutants cause hazardous tachyarrhythmia and decreased heart rate variability consistent with sympathoexcitation. Nevertheless, in healthy animals and humans, inhalation of pollutants and irritants evokes parasympathetic‐mediated bradycardia. Here, we have compared the changes in blood pressure and the cardiac cycle in normotensive Wistar‐Kyoto rats (WK) and Spontaneously Hypertensive rats (SH) upon inhalation of allyl isothiocyanate (AITC), a selective agonist of TRPA1, the major pollutant‐sensor expressed on airway nociceptive nerves. Studies were performed in conscious, unrestrained 15‐week old rats using radiotelemetry. Resting mean arterial blood pressure were 188 mmHg and 120 mmHg for SH and WK, respectively. Resting heart rates were not different between the strains (~360 bpm). Inhalation of AITC caused substantial bradycardia and AV nodal block in WK, which was prevented by the muscarinic inhibitor atropine. In SH, inhalation of AITC caused bouts of brady‐tachycardia accompanied by both AV block and premature ventricular contractions (PVCs). Atropine prevented the evoked bradycardia and AV block in SH, exposing greater reflex tachycardia. The beta1‐adrenoceptor antagonist atenolol prevented AITC‐evoked tachycardia and PVCs in SH. AITC caused much greater hypertension in SH compared to WK. 24 hour treatment of captopril, the angiotensin converting enzyme inhibitor, normalized blood pressure in SH. Nevertheless, captopril had no effect on AITC‐evoked reflexes in SH. These data indicate that pre‐existing chronic hypertension remodels pollution‐sensitive pulmonary‐cardiac reflexes from parasympathetic towards sympathoexcitation. The remodeled reflex is not dependent on preservation of the hypertension.Support or Funding InformationAmerican Heart Association Grant‐in‐Aid (16GRNT31460004)
Inflammation and Impaired α2‐Adrenergic Receptor‐Mediated Inhibition of Ca2+ Channels Contribute to Hypertension in DOCA‐Salt but not Obese Dahl SS Rats
Authors: Mui Ryan K , Fernandes Roxanne N , Garver Hannah G , Fink Gregory D , Xu Hui , Galligan James J 
Published: November 2023

IntroductionInflammation is associated with increased sympathetic nerve activity in hypertension. Inhibition of norepinephrine (NE) release from nerve terminals occurs through prejunctional α2‐adrenergic receptor (α2AR)‐mediated inhibition of N‐type voltage‐gated Ca2+ channels. Inflammation has been implicated in adrenergic receptor desensitization. Desensitization of α2AR occurs through G‐protein receptor kinases (GRKs) that uncouple receptors from G‐proteins. We tested the hypothesis that DOCA‐salt and a high fat diet (HFD) causes inflammation and impaired inhibition of Ca2+ channels through desensitization of prejunctional α2ARs.MethodsUniphrectomized rats were given water (SHAM) or 200mg/kg DOCA (sc) and 1% NaCl/0.2% KCl water (DOCA) for 4 weeks. Dahl salt‐sensitive (Dahl SS) rats were given a high fat diet (HFD, 60% kcal from fat) or normal fat diet (NFD, 10% kcal from fat) for 26 weeks. Inflammation was assessed by macrophage staining (CD163) in mesenteric arteries and qRT‐PCR of celiac/splanchnic ganglia for MCP‐1, TNFα, and IL‐6. Whole cell patch clamp was used to measure α2AR‐mediated inhibition of Ca2+ channels using NE and UK1430 (agonists) and yohimbine (antagonist). mRNA levels of α2AR (2A, 2B, 2C) and GRK (2,3,5) in celiac/splanchnic ganglia were measured by qRT‐PCR. Paroxetine was used to inhibit GRK2 vs. fluoxetine (control). Clodronate‐embedded liposomes were used to deplete macrophages.ResultsDOCA‐salt and HFD treatment caused hypertension vs. controls. Vascular macrophage infiltration and mRNA levels of MCP‐1, TNFα, and IL‐6 mRNA were significantly higher in DOCA‐salt vs. SHAM rats, but not in HFD vs. NFD Dahl SS rats. DOCA‐salt and HFD treatment impaired α2AR‐mediated inhibition of Ca2+ channels by NE and UK14304 treatment in celiac ganglion neurons. Yohimbine blocked the effects of NE in all neurons. There were no differences in α2AR (2A,2B,2C) mRNA levels in DOCA‐salt and HFD vs. controls. GRK2 mRNA levels were higher in DOCA‐salt vs. SHAM rats, but lower in HFD vs. NFD Dahl SS rats. Paroxetine did not increase α2AR‐mediated inhibition of Ca2+ channels in neurons from DOCA‐salt rats vs. fluoxetine treatment. Macrophage depletion preserved α2AR function and lowered blood pressure in DOCA‐salt rats.ConclusionsInflammation and macrophage‐associated impairment of α2AR‐mediated inhibition of Ca2+ channels occur in DOCA‐salt but not HFD‐Dahl SS rats. DOCA‐salt and HFD treatment does not affect α2AR mRNA expression. In DOCA‐salt rats, α2AR dysfunction does not occur via GRK‐dependent desensitization. In HFD‐Dahl SS rats, equivalent α2AR function to NFD rats may be attributed to decreased GRK2 expression.Support or Funding InformationSupported by NIH 2P01HL070687 and American Heart Association (15PRE25090218)
GABA and Glycine: Fine Tuning for Inhibitory Control of Brainstem RVLM Neurons
Authors: Gao Hong , Derbenev Andrei 
Published: November 2023

Presympathetic neurons in the rostral ventrolateral medulla (RVLM) are best known for their contribution to the control of sympathetic nervous system and homeostatic functions of the body. Both glycine and GABA were identified as fast inhibitory neurotransmitters in the RVLM. GABA is essential for the control of the excitability of neurons, while glycine also inhibits neurons in the RVLM, and thus control sympathetic output. Despite the critical role of GABA and glycine as inhibitory neurotransmitters, surprisingly little is known about the mechanisms of GABA and glycine release and/or co‐release. Using whole‐cell patch‐clamp recordings from presympathetic neurons identified with PRV‐152, we examined GABAergic and glycinergic inhibitory mechanisms in rat brainstem slices containing RVLM neurons. We tested the hypothesis that the release of glycine is associated with the activity of neuronal network. We found that inhibitory postsynaptic currents (IPSCs) recorded from RVLM neurons composed from both GABAergic and glycinergic events. In steady state conditions, GABA is the predominant inhibitory neurotransmitter in the RVLM. Interestingly, after activation of the inhibitory network, we found that GABAergic and glycinergic neurotransmission were reversed. Under resting condition, the proportion of glycinergic IPSCs was less than 10% of the total IPSCs. Activation of the inhibitory network produced saturation of inhibitory events mediated by GABA and increased the average frequency of glycine‐mediated IPSCs. After network activation, glycinergic IPSCs represent more than half of the total IPSCs in the RVLM. Our data suggest that after saturation of GABA, glycinergic inhibition provides a secondary synaptic inhibition in presympathetic RVLM neurons. This novel mechanism has the potential for fine tuning of the sympathetic output controlling homeostatic functions.Support or Funding InformationSupported by NHLBI R01HL122829
Neuromuscular inactivity of the respiratory control system during overwintering in bullfrogs, Lithobates catesbeianus
Authors: Santin Joseph M. , Hartzler Lynn 
Published: November 2023

In clinical disorders, inactivity typically results in loss of normal neuromuscular function. In contrast, hibernating, estivating, and overwintering animals use compensatory mechanisms and/or avoidance strategies to preserve motor function in the face of inevitable dormancy. Semiaquatic frogs typically overwinter in ponds that may be covered by ice and, therefore, do not regulate lung breathing for weeks to months. Despite a lack of lung breathing, motor function of the respiratory system in American bullfrogs, Lithobates catesbeianus, remains fully competent during the winter and operates adequately to match ventilation to metabolism in early spring. Unlike overwintering hibernators with unloaded limb muscles and putatively inactive locomotor systems, frogs may continue producing respiratory motor activity during cold‐submergence to maintain a functional respiratory motor system. Inactivity avoidance could occur because anuran amphibians have respiratory mechanics that, counterintuitively, can produce ventilatory motor patterns under water. Therefore, we hypothesized that bullfrogs generate respiratory motor patterns during cold‐submergence as a mechanism to avoid disuse and preserve motor performance. To test this hypothesis, we measured activity of respiratory muscles (buccal floor compressor, posterior m. intermandibularis and glottal dilator, m. dilator laryngis) via chronic electromyography (EMG) in freely behaving bullfrogs at 20°C and while submerged at 2°C (n=8). As expected, activation of the glottal dilators coincided with large amplitude activity of the buccal floor compressors to produce lung ventilation. In contrast, small amplitude oscillatory activity of the buccal floor compressors occurred without activation of glottal dilators, indicative of buccal ventilation. We found that bullfrogs took 5.5±1.4 breaths per minute when surfacing at 20°C, and we confirmed that underwater “ventilation cycles” occur at a rate of 1.7±0.2 events per minute at 20°C. At 2°C, bullfrogs neither surfaced to ventilate their lungs (2°C vs. 20°C; p<0.0001; one‐way ANOVA), nor did they activate either group of respiratory muscles when submerged at 2°C for 10 days (2°C vs. 20°C; p<0.0001; one‐way ANOVA). Tonic activity characteristic of resting muscle tone did not change after submergence at 2°C in buccal floor compressors or the glottal dilators, for at least 10 days (buccal floor, p=0.4, one‐way ANOVA; glottal dilator, p=0.55, one‐way ANOVA). In conclusion, bullfrogs experience bona fide respiratory motor inactivity during cold‐submergence associated with overwintering. Underwater neuromuscular activation is, therefore, an unlikely mechanism to preserve respiratory motor function after overwintering, but normal function may be maintained through compensation at the level of the motor network.Support or Funding InformationNational Science Foundation grant IOS‐1257338Wright State Research CouncilWright State Biomedical Science PhD Program