bluuebunny/crossref_metadata_2025_split huggingface dataset:
Knockdown of Tim23 In‐Vivo Results in the Activation of the Mitochondrial Unfolded Protein Response
Authors: Oliveira Ashley Nicole , Hood David 
Published: November 2023

Mitochondria rely heavily on the tight coordination of the nuclear and mitochondrial genomes. Disruption of this regulation has been shown in lower order organisms to result in a mito‐nuclear imbalance in which holenzymes are unable to assume mature stoichiometry. This lack of coordination between nuclear and mitochondrially encoded subunits resulting in orphaned subunits is an activator of the mitochondrial unfolded protein response (UPRmt). The UPRmt is a highly conserved quality control mechanism that strives to achieve proteostasis by refolding or degrading misfolded proteins as well as misassembled complexes. This process is well characterized in c. elegans however, the UPRmt and its retrograde signals are poorly understood in mammals. Thus we sought to induce the UPRmt in‐vivo‐in a mammalian model to better characterize this stress response. In order to do so, C57BL/6 mice were injected once a day for 3 days with an antisense oligonucleotide (In‐Vivo Morpholino) targeted to Tim23, the major channel of the inner membrane, to perturb the genomic coordination. Following Tim23 Morpholino treatment, Tim23 protein content was significantly reduced by 50%. The consequence was a 60% reduction of protein import into the mitochondrial matrix. As a result, mitochondrial chaperone cpn10 was significantly elevated by 30% and the transcription factor ATF5 also demonstrated a strong trend to increase, suggesting that the UPRmt was activated following Tim23 knockdown. Mitochondrial respiration and ROS emission was also measured to determine whether Tim23 knockdown resulted in mitochondrial dysfunction. However, no differences were found suggesting that the stress imposed is sufficient to induce the UPRmt without disrupting basic mitochondrial functions. The second aim of this study was to investigate the role of mitochondrial proteolytic byproducts in mediating retrograde signaling. Peptides released from the mitochondria following basal proteolysis were isolated and incubated with import reactions. Our results demonstrate a dose‐ and time‐dependent inhibition of import with the addition of peptides, such that import was reduced by 48% with the addition of 6ug of peptides for 30 minutes. This suggests that mitochondrial proteolytic byproducts can exert an inhibitory effect on the protein import pathway, to inhibit excessive protein import as a negative feedback mechanism. The inhibition of import into the organelle may also serve a retrograde function, to modify nuclear gene expression and improve organelle folding capacity, or alter the expression of protein import machinery components.Support or Funding InformationThis work is supported by the Natural Science and Engineering Research Council (NSERC) of Canada.
MicroRNA in Muscle: Characterising the Powerlifter Phenotype
Authors: D'Souza R. F. , Bjornsen T. , Aasen K. M. , Raastad T. , Mitchell C. J. , Cameron‐Smith D. 
Published: November 2023

Skeletal muscle has a remarkable capacity to adapt in response to imposed external loads. Powerlifters are the epitome of this adaptation and are able to generate extremely high muscular forces. The molecular mechanisms underpinning the significant capacity for force generation and hypertrophy are unclear. MicroRNAs (miRs) are short non‐coding RNA sequences that control gene expression via promotion of transcript breakdown and/or translational inhibition. Differences in miR expression at rest may account for phenotypic differences in muscle mass and function between powerlifters and untrained age‐matched controls.The primary object of this study was to characterize the expression profiles of a subset of miRs known to exert an influence on key aspects of myogenic regulation in the muscles of highly trained powerlifters. Muscle biopsies were obtained from the vastus lateralis of 17 national level powerlifters (25.1 ± 5.8 years) and 17 untrained controls (24.1 ± 2.0 years). The powerlifters were stronger than the controls (isometric knee extensions: 297.9 ± 56.1 Nm, 193.6 ± 46.6 Nm, respectively p <0.001), and also had bigger muscle fibres (type I CSA 8869 ± 1366 μm2 compared to 4196 ± 9632 μm2 p<0.001 and type II CSA 10636 ± 2029 μm2 compared to 5327 ± 1342 μm2 p<0.001). Of the 15 miRs species analysed, 12 were differently expressed between groups. 7 were upregulated in powerlifters; miR ‐15a (p<0.001), ‐16 (p=0.008), ‐23a (p<0.001), ‐23b (p<0.001), ‐451a (p=0.012), ‐30b (p=0.010) and ‐206 (p=0.032). Conversely, 5 were reduced in the powerlifters; miR‐486 (p=0.002), ‐499 (p=0.018), ‐126 (p<0.001), ‐133a (p=0.001) and ‐1 (p=0.013). Whilst, miRs‐208a, ‐208b and ‐145 did not differ between groups.Powerlifters have larger muscle fibres capable of producing greater contractile force. The unique miR expression profiles of powerlifters compared to the healthy untrained controls indicates miRs may be a component of the post‐transcriptional regulation necessary for the maintenance of increased muscle mass and strength. The miRs of interest have putative roles in muscle atrophy, hypertrophy and angiogenesis indicating a possible involvement in regulation of muscle mass and contractile capacity.
IL‐15 Activates the Jak3/STAT3 Signaling Pathway to Mediate Glucose Uptake in Skeletal Muscle Cells
Authors: Abbott Marcia J , Krolopp James E , Thornton Shantae M 
Published: November 2023

Myokines are specialized cytokines that are secreted from skeletal muscle (SKM) in response to metabolic stimuli, such as exercise. Interleukin‐15 (IL‐15) is a myokine with potential to reduce obesity and increase lean mass through induction of metabolic processes. It has been previously shown that IL‐15 acts to increase glucose uptake in SKM cells. However, the downstream signals orchestrating the link between IL‐15 signaling and glucose uptake have not been fully explored. Here we employed the mouse SKM C2C12 cell line to examine potential downstream targets of IL‐15‐induced alterations in glucose uptake. Following differentiation, C2C12 cells were treated overnight with 100 ng/ml of IL‐15. Activation of factors associated with glucose metabolism (Akt and AMPK) and known downstream targets of IL‐15 (Jak1, Jak3, STAT3, and STAT5) were assessed with IL‐15 stimulation. IL‐15 stimulated glucose uptake and GLUT4 translocation to the plasma membrane. IL‐15 treatment had no effect on phospho‐Akt, phospho‐Akt substrates, phospho‐AMPK, phospho‐Jak1, or phospho‐STAT5. However, with IL‐15, phospho‐Jak3 and phospho‐STAT3 levels were increased along with increased interaction of Jak3 and STAT3. Additionally, IL‐15 induced a translocation of phospho‐STAT3 from the cytoplasm to the nucleus. We have evidence that a mediator of glucose uptake, HIF1α, expression was dependent on IL‐15 induced STAT3 activation. Finally, upon inhibition of STAT3 the positive effects of IL‐15 on glucose uptake and GLUT4 translocation were abolished. Taken together, we provide evidence for a novel signaling pathway for IL‐15 acting through Jak3/STAT3 to regulate glucose metabolism.Support or Funding InformationThis work was supported by Chapman University, the American College of Sports Medicine Foundation, and the American Heart Association Grant #16SDG30680003 (MJ Abbott).
Mitochondrial respiration is fiber‐type specific in skeletal muscles
Authors: Lin Cheng‐Hsien , Chen Chiao‐nan 
Published: November 2023

IntroductionMitochondria are the power houses of the cells and they also play critical roles in the cellular oxidative stress and apoptosis. It is known that mitochondrial density and morphology are fiber‐type specific. Based on differential contractile properties of different types of skeletal muscles, we hypothesized that the mitochondria respiration is fiber‐type specific. The aim of the study is to compare and contrast mitochondria respiration between type I and type II muscles.MethodSoleus (predominantly composed of type I fibers) and plantaris (predominantly composed of type II fibers) muscles were taken from adult rats. Mitochondrial respiration was determined in duplicate by a high‐resolution respirometry OROBOROS Oxygraph‐2k (O2k). The mitochondrial substrate‐uncoupler‐inhibitor titration (SUIT) protocol was used to determine mitochondrial oxygen consumption rate (O2 flux) of permeabilized myofibers. Paired t test was used to compare parameters between soleus and plantaris muscles.ResultsWe found that basal mitochondrial respiration (i.e. O2 flux_ complex I plus complex II) and leak of permeabilized muscle fibers was similar between soleus and plantaris muscles. Similarly, mitochondrial coupling control ratio defined by leak divided by basal mitochondrial respiration (i.e. leak/O2 flux_ complex I plus complex II) is similar between soleus and plantaris muscles. Maximal electron transport system capacity (maximal mitochondrial respiration) of soleus muscles was greater than that of plantaris muscles. In addition, mitochondrial respiratory reserve capacity defined by subtracting basal mitochondrial respiration from maximal mitochondrial respiration was greater in soleus muscles than in plantaris muscles.ConclusionBasal mitochondrial respiration and leak are similar between type I and type II muscles. However, mitochondria in type I muscles have greater respiratory reserve compared to that in type II muscles. This fiber‐type specific mitochondrial respiration is likely associated with the differential fuel metabolism and contractile properties of muscle fibers.
Sympathetic Neural Control in Chronic Insomnia
Authors: Carter Jason R. , Grimaldi Daniela , Fonkoue Ida T. , Medalie Lisa , Mokhlesi Babak , Van Cauter Eve 
Published: November 2023

Heightened sympathetic neural activity and impaired baroreflex function are known contributors to hypertension and cardiovascular risk. Recent epidemiological studies report an association between chronic insomnia and hypertension. In the present study, we examined sympathetic neural and cardiovascular regulation in clinically diagnosed insomniacs and controls. Consistent with the hyperarousal theory of insomnia, we hypothesized that insomniacs would demonstrate higher sympathetic neural outflow and blunted baroreflex control when compared to matched controls. Thirteen insomniacs (40 ± 4 years, 24 ± 1 kg/m2) and 15 matched controls (35 ± 3 years, 26 ± 1 kg/m2; p>0.05) participated in an overnight laboratory polysomnography to exclude obstructive sleep apnea and other sleep disorders, two weeks of at‐home actigraphy, and an overnight laboratory visit with an autonomic function test the subsequent morning. The autonomic function test included simultaneous recordings of heart rate (electrocardiogram), beat‐to‐beat blood pressure (finger plethysmography), and muscle sympathetic nerve activity (MSNA; microneurography) during 10 min supine baseline. Baseline systolic arterial pressure (110 ± 5 vs. 113 ± 4 mmHg; p=0.673), diastolic arterial pressure (69 ± 3 vs. 66 ± 2 mmHg; p=0.424), heart rate (64 ± 3 vs. 59 ± 2 mmHg; p=0.169), and MSNA (23 ± 3 vs. 25 ± 3 bursts/min; p=0.635) were not different between insomniacs and controls. In contrast, spontaneous sympathetic baroreflex sensitivity (BRS) was significantly blunted in insomniacs when compared to controls (−2.1 ± 0.3 vs. −4.3 ± 0.4 bursts/100 heart beats/mmHg; p<0.001). Cardiovagal BRS was not different between groups when assessed as either up‐up (23 ± 4 vs. 25 ± 6 ms/mmHg; p=0.843) or down‐down (25 ±5 vs. 25 ± 5 ms/mmHg; p=0.955) sequencing methods. In conclusion, insomniacs demonstrated similar levels of MSNA, but substantially blunted sympathetic BRS, at rest when compared to matched controls. These findings support growing evidence of increased risk of hypertension with chronic insomnia.Support or Funding InformationSupported by Merck Investigators Studies Program.
Sleep Restriction Degrades Local Immune Response of Experimental Wounds
Authors: Wilson Marques A , Young Andrew J , Montain Scott J , Smith Tracey J 
Published: November 2023

The suction blister model creates experimental skin wounds and permits evaluation of local immune response and wound healing. Sleep restriction negatively affects systemic immune function, e.g., natural killer cell activity, suppressed interleukin‐2 production and increased levels of circulating proinflammatory cytokines; however, the impact of sleep restriction on local immune response at experimental wound sites has not been described. This cross‐sectional study assessed the effect of sleep restriction on wound exudate cytokine concentrations after skin blister formation. Up to 8 blisters (~30 mm2) were induced viasuction on participant's forearm either after 5 nights of adequate sleep (AS,7–9‐h sleep per night confirmed via activity monitors) or on the second day of a 3‐d sleep restriction period (SR, monitored in laboratory with ~2‐h sleep pernight). The top layer of blisters was removed to reveal up to 8 wounds. Wound exudate was sampled at 4, 7 and 24‐h post blistering to assess cytokine response via multiplex assay and area‐under‐the‐curve with respect to baseline cytokine concentrations (AUCi) was calculated. Skin barrier restoration was assessed by transepidermal water loss, measured daily until values were within 90% of unbroken skin. Data, analyzed with mixed models analysis of variance and independent samples t‐tests, is reported for the sixteen (AS: 23 ± 5 years [mean±SD]) and twenty (SR: 21 ± 4 years) study completers. Sleep duration in the 5‐days leading up to either the blister procedure (AS) or the sleep restriction period (SR) was not different between groups (7.99 ± 0.5 hrs·d−1 and 7.71 ± 0.67 hrs·d−1, respectively, P = 0.18). Wound exudate concentrations of IL6, IL8, MIP1α, MIP1βand TNFα significantly increased over time for both AS and SR (p < 0.05);and, concentrations of IL6 and IL8 were higher for AS compared to SR at 7‐h (P= 0.03 and 0.004, respectively). The AUCi was higher for AS compared to SR with regard to IL8 (log10, 5.1 ± 0.2 and 4.9 ± 0.2, respectively, P = 0.03), but not other cytokines. Skin barrier restoration was shorter for AS compared to SR: 4.2 ± 0.9 and 5.0 ± 0.9 days, respectively (P = 0.02). These data support the hypothesis that relatively modest sleep disruption degrades immune response at the wound site and delays wound healing. Interventions to ameliorate decrements in immunefunction and wound healing in response to sleep restriction deserve exploration.Disclaimer: The views expressed in this abstract are those of the authors and do not reflect the official policy of the Department of Army, Department of Defense, or the U.S. Government.Support or Funding InformationFunded by the Medical Research and Materiel Command, Aberdeen Proving Ground, Maryland.
Developmental Exposure to Indoor Flame Retardants Produces Diabetic Phenotype in Adult Female C57BL6 Mice
Authors: Kozlova Elena , Krum Julia Meagan , Basappa Karthik , Uddin Syed , Curras‐Collazo Margarita C 
Published: November 2023

Polybrominated diphenyl ethers are a group of flame‐retardant organohalogen pollutants that act as endocrine and neuroendocrine disrupting chemicals. In humans, exposure to brominated flame retardants or other environmentally persistent organic pollutants (POPs) such as polychlorinated biphenyls (PCBs) has been associated with increasing trends of diabetes and metabolic disease (Gray et al. 2013; Baker et al. 2013; Lim et al, 2008; Lee et al, 2006). POPs may disrupt metabolic homeostasis through chronic low‐level exposure and bio‐accumulation in liver, adipose tissue and brain (Zhang et al, 2016; Turyk et al, 2015). However, the effects of PBDEs on metabolic processes are poorly understood. In this study we examined the effects of gestational and lactational exposure to the industrial PBDE mixture DE‐71 on glucose tolerance test (GTT), insulin tolerance test (ITT), and liver lipid content in C57BL/6 female offspring in adulthood (128–147 days; 17.1–22 g). We also examined intestinal permeability since intestinal‐derived bacterial products entering the bloodstream may cause inflammation, liver disease that may contribute to obesity and diabetes (Turner, 2009). Mice were exposed to environmentally relevant doses of PBDEs for 10 weeks (pre‐conception: 4 weeks; gestation: 3 weeks; lactation: 3 weeks). Daily dosing consisted of low dose (0.1 mg/kg/d), high dose (0.4 mg/kg/d), or corn oil vehicle (control) via ingestion of infused corn flakes. GTT results revealed that blood glucose levels normalized to fasting levels were significantly elevated at 30 and 60 min post injection of glucose (2.0 g/kg) in LD mice relative to oil vehicle controls (p<0.0001, n=20). ITT results showed a significantly decreased sensitivity to insulin (0.5 U/kg) at post‐injection time points from 15–120 min for LD and 15–90 min for HD female offspring (p<0.05 to 0.0001, n=19). Mean levels of liver lipids were significantly elevated in LD female offspring compared to controls (p<0.05, n= 18). To determine if PBDE‐exposed offspring showed altered intestinal permeability, mice were orally gavaged with 60 mg/kg FITC‐dextran (mol. wt. 3,000–5,000; FD‐4, Sigma) and fluorescence measured in the blood 4 hr later by fluorimetry (excitation 490 nm, emission 530 nm). PBDE at HD had an apparent effect on elevated plasma FITC levels but the effects were not significant indicating that PBDEs may not produce their effects via changes in intestinal barrier integrity. These results indicate that mice perinatally exposed to PBDEs (0.1 mg/kg dose) display abnormal glucose and lipid metabolic parameters indicative of a diabetic phenotype.Support or Funding InformationSupported by University of California COR grant and UCMEXUS.
SPAK Kinase Modulates Energy Expenditure and Thermogenesis in Mice Fed a High‐fat Diet
Authors: Torre‐Villalvazo Ivan , Cervantes‐Perez Luz Graciela , Noriega Lilia Guadalupe , Jimenez José Victor , Uribe Norma , Torres Nimbe , Bobadilla Norma Araceli , Tovar Armando , Gamba Gerardo 
Published: November 2023

Body weight regulation and glucose homeostasis are controlled by central and peripheral mechanisms. In the central nervous system, hypothalamic nuclei trough neuronal axes that release GABA modulate energy expenditure and thermogenesis and the peripheral glucose metabolism is controlled in part by pancreatic insulin secretion from β‐cells. Interestingly, the intracellular chloride concentration ([Cl−]i) is involved in the modulation of both processes, the GABA signaling and insulin secretion. The activity of the electroneutral cation coupled chloride cotransporters (CCC) is critical to define the [Cl−]i. Phosphorylation of the CCC members promotes Cl− influx, while dephosphorylation promotes Cl− efflux. The kinase that phosphorylates the CCCs is known as SPAK (STE20‐proline alanine rich kinase). The SPAK activity modulates the [Cl−]i by controlling the activity of the CCCs. In this regards, the homozygous SPAK‐Knockin mice lacking the threonine 243 of the T‐loop required for its activation (SPAKT243A/T243A) exhibit no SPAK activity and thus a marked decrease in CCCs phosphorylation. Here, to analyze the role of SPAK in metabolic homeostasis we fed wild type and SPAKT243A/T243A mice a high‐fat diet (HFD) for 17 weeks to evaluate weight gain, metabolic variables, energy expenditure, glucose tolerance, as well as, liver, pancreatic and adipose tissue histology and histochemistry. Food consumption was similar among groups during the feeding period. The wild type mice, however, gained 15.1 ± 0.8 g, whereas the SPAKT243A/T243A mice gained only 10.2 ± 2.0 g (p<0.01). At the end of the study, in contrast to wild type mice, SPAKT243A/T243A mice exhibited significantly lower fat mass, cholesterol, triglycerides and leptin levels, as well as improved insulin secretion and glucose tolerance. SPAKT243A/T243A mice did not develop hepatic steatosis and pancreatic islets hypertrophy as wild type did. The enhanced metabolic function of SPAKT243A/T243A mice was associated with increased whole body oxygen consumption and augmented fat oxidation. The molecular mechanisms responsible for this phenotype involve improved pancreatic β‐cell function, augmented skeletal muscle mitochondrial activity and increased brown adipose tissue UCP1‐mediated thermogenesis. Our data show that the absence of SPAK activity in mice is associated with an obesity resistant phenotype when exposed to HFD. These observations suggest that modulation of SPAK activity could be a potential new therapeutic avenue for obesity and glucose metabolism disorders.Support or Funding InformationGrant No. 23, of the Fronteras de la Ciencia program of Mexican Council for Science and Technology (CONACYT)
The Evf2 enhancer lncRNA links chromosomal interactions and interneuron diversity
Authors: Kohtz Jhumku , Cajigas Ivelisse , Swyter Kelsey R , Bastidas Monique , Chakraborty Abhijit , Morris Elizabeth , Ay Ferhat 
Published: November 2023

Understanding how genes are selectively regulated during development is a major goal in biology. While DNA enhancers selectively regulate genes at a distance, mechanisms regulating long distance enhancer interactions are only beginning to be understood. Our previous work reported transcriptional activity by Evf2, an enhancer long non‐coding RNA (lncRNA) transcribed from the Dlx5/6 ultraconserved enhancer (Dlx5/6ei)1. Evf2 regulates adjacent chr6 genes Dlx5/6, recruiting both activators and repressors to Dlx5/6ei, and forms a large ribonucleoprotein complex (Evf2‐RNP, ~79 proteins) that contains the DLX1 homeodomain transcription factor and chromatin remodelers2,3,4. Promiscuous interactions between Evf2 and chromatin remodelers reveal RNA‐mediated direct inhibition of BRG1(SMARCA4) ATPase and remodeling activities4. Thus, enhancer RNAs can regulate enhancer activity by providing a scaffold for multiple promiscuous RNA binding proteins, and directly regulating enzymatic activity. Here, we show evidence supporting that Evf2 controls chromosome‐wide enhancer interactions and histone modifications, selectively regulating genes located in a ~27Mb region of chr6 (Evf2‐chr6 targets). These data support the idea and that while Evf2 plays a major role in chromosome topology, only a subset of Evf2‐dependent enhancer interactions contribute to gene regulation. Evf2 loss, truncation, and rescue distinguish between the roles of the Evf2‐5′ ultraconserved enhancer‐containing region and trans/cis mechanisms that regulate Evf2‐chr6 targets. Together, this work identifies a novel network of interneuron subtype gene regulation that links enhancer lncRNA directed chromosomal interactions and interneuron diversity in the embryonic mouse brain.Support or Funding InformationNIMH R01MH094653 to J.D.K