Characterization of sclerostin’s response within white adipose tissue to an obesogenic diet at rest and in response to acute exercise in male mice

This study examined the effect of a high-fat diet (HFD) on sclerostin content within subcutaneous inguinal visceral white adipose tissue (iWAT), and visceral epididymal WAT (eWAT) depots at rest and in response to acute aerobic exercise. Male C57BL/6 mice (n=40, 18 weeks of age) underwent 10 weeks of either a low-fat diet (LFD) or HFD. Within each diet group, mice were assigned to either remain sedentary (SED) or perform 2h of endurance treadmill exercise at 15 m·min-1 with 5° incline (EX), creating 4 groups: LFD+SED (N=10), LFD+EX (N=10), HFD+SED (N=10), and HFD+EX (N=10). Serum and WAT depots were collected 2h post-exercise. Serum sclerostin showed a diet-by-exercise interaction, reflecting HFD+EX mice having higher concentration than HFD-SED (+31%, p=0.03), and LFD mice being unresponsive to exercise. iWAT sclerostin content decreased post-exercise in both 28 kDa (-31%, p=0.04) and 30 kDa bands (-36%, main effect for exercise, p=0.02). iWAT b-catenin (+44%, p=0.03) and GSK3b content were elevated in HFD mice compared to LFD (+128%, main effect for diet, p=0.005). Monomeric sclerostin content was abolished in eWAT of HFD mice (-96%, main effect for diet, p<0.0001), was only detectable as a 30 kDa band in LFD mice and was unresponsive to exercise. b-catenin and GSK3b were both unresponsive to diet and exercise within eWAT. These results characterized sclerostin’s mobilization to WAT depots in response to acute exercise, which appears to be specific to a reduction in iWAT and identified a differential regulation of sclerostin’s form/post-translational modifications depending on diet and WAT depot.This research was funded by the Natural Sciences and Engineering Research Council of Canada (NSERC grant to P. Klentrou # 2020-00014). N. Kurgan, B. Baranowski and Joshua Stoikos hold NSERC doctoral scholarships

SMAD1/5 signaling in the early equine placenta regulates trophoblast differentiation and chorionic gonadotropin secretion.

TGFβ superfamily proteins, acting via SMAD (Sma- and Mad-related protein)2/3 pathways, regulate placental function; however, the role of SMAD1/5/8 pathway in the placenta is unknown. This study investigated the functional role of bone morphogenetic protein (BMP)4 signaling through SMAD1/5 in terminal differentiation of primary chorionic gonadotropin (CG)-secreting trophoblast. Primary equine trophoblast cells or placental tissues were isolated from day 27-34 equine conceptuses. Detected by microarray, RT-PCR, and quantitative RT-PCR, equine chorionic girdle trophoblast showed increased gene expression of receptors that bind BMP4. BMP4 mRNA expression was 20- to 60-fold higher in placental tissues adjacent to the chorionic girdle compared with chorionic girdle itself, suggesting BMP4 acts primarily in a paracrine manner on the chorionic girdle. Stimulation of chorionic girdle-trophoblast cells with BMP4 resulted in a dose-dependent and developmental stage-dependent increase in total number and proportion of terminally differentiated binucleate cells. Furthermore, BMP4 treatment induced non-CG-secreting day 31 chorionic girdle trophoblast cells to secrete CG, confirming a specific functional response to BMP4 stimulation. Inhibition of SMAD2/3 signaling combined with BMP4 treatment further enhanced differentiation of trophoblast cells. Phospho-SMAD1/5, but not phospho-SMAD2, expression as determined by Western blotting was tightly regulated during chorionic girdle trophoblast differentiation in vivo, with peak expression of phospho-SMAD1/5 in vivo noted at day 31 corresponding to maximal differentiation response of trophoblast in vitro. Collectively, these experiments demonstrate the involvement of BMP4-dependent pathways in the regulation of equine trophoblast differentiation in vivo and primary trophoblast differentiation in vitro via activation of SMAD1/5 pathway, a previously unreported mechanism of TGFβ signaling in the mammalian placenta

A Low-Therapeutic Dose of Lithium Inhibits GSK3 and Enhances Myoblast Fusion in C2C12 Cells

Glycogen synthase kinase 3 (GSK3) slows myogenic differentiation and myoblast fusion partly by inhibiting the Wnt/β-catenin signaling pathway. Lithium, a common medication for bipolar disorder, inhibits GSK3 via Mg+ competition and increased Ser21 (GSK3α) or Ser9 (GSK3β) phosphorylation, leading to enhanced myoblast fusion and myogenic differentiation. However, previous studies demonstrating the effect of lithium on GSK3 have used concentrations up to 10 mM, which greatly exceeds concentrations measured in the serum of patients being treated for bipolar disorder (0.5–1.2 mM). Here, we determined whether a low-therapeutic (0.5 mM) dose of lithium could promote myoblast fusion and myogenic differentiation in C2C12 cells. C2C12 myotubes differentiated for three days in media containing 0.5 mM lithium chloride (LiCl) had significantly higher GSK3β (ser9) and GSK3α (ser21) phosphorylation compared with control myotubes differentiated in the same media without LiCl (+2–2.5 fold, p < 0.05), a result associated with an increase in total β-catenin. To further demonstrate that 0.5 mM LiCl inhibited GSK3 activity, we also developed a novel GSK3-specific activity assay. Using this enzyme-linked spectrophotometric assay, we showed that 0.5 mM LiCl-treated myotubes had significantly reduced GSK3 activity (−86%, p < 0.001). Correspondingly, 0.5 mM LiCl treated myotubes had a higher myoblast fusion index compared with control (p < 0.001) and significantly higher levels of markers of myogenesis (myogenin, +3-fold, p < 0.001) and myogenic differentiation (myosin heavy chain, +10-fold, p < 0.001). These results indicate that a low-therapeutic dose of LiCl is sufficient to promote myoblast fusion and myogenic differentiation in muscle cells, which has implications for the treatment of several myopathic conditionsBrock University Library Open Access Publishing Fun

Spectral purification of single-frequency Stokes pulses in doubly resonant integrated diamond resonators

Pulsed spectrally pure light is required for applications in high-resolution spectroscopy, optical coherent communications, and quantum technologies. In this work, we report on the efficient generation of high peak power, single-frequency, and tunable nanosecond pulses utilizing stimulated scattering, with an increased spectral brightness by exploiting double resonances in an integrated diamond Raman resonator. The device is based on a miniature monolithic Fabry–Perot design pumped by a milliwatt-class average power Q-switched single-frequency pulsed laser at 532 nm. Our device was capable of enhancing the peak spectral brightness by greater than three times compared with conventional singly resonant diamond Raman lasers by tuning the effective resonator length at pump and Stokes wavelengths simultaneously. Our results facilitate the integration of pulsed and power scalable single frequency sources into hybrid photonic integrated platforms with a broad range of applications

Monolithic diamond Raman resonators for high resolution spectroscopy

Tunable and spectrally pure lasers at visible wavelengths are key tools for many applications in physics, metrology and quantum technology. Integrating these laser sources on wafer-scaled devices is necessary for scaling the technology, allowing for powerful quantum tools. Current implementations however, are composed by complex, bulky systems that are in no way suitable to be used in the mentioned applications. To tackle this, we propose monolithic diamond Raman resonators as scalable, tunable, single-frequency laser sources. In these resonators, lasing happens through stimulated Raman scattering, which under certain conditions allows for the production of narrow-linewidth Stokes laser fields. Diamond-bulk temperature changes are used here to tune the Stokes center frequency and a model is developed to predict its performance. Moreover the rate of change of the Stokes center frequency with temperature allows for precise measurements of the thermo-optic coefficient of diamond, and also shines light on the temperature-dependent average phonon frequency of the material. Furthermore, when pumped by single mode lasers, we study the periodic narrowing of the single-mode profile of the output laser due to double resonance which is modeled and analysed. Lastly, we demonstrate its use for high-resolution spectroscopy showing an achieved spectral resolution of 0.51~GHz, establishing its suitability for precise measurements and ion excitation, and paving the way for a scalable photonic source for quantum technology applications

The Effect of Sclerostin on Myotropic Response to Exercise

This study is the first to examine the effect of exogenous sclerostin injection on myotropic responses to sedentary behaviour and an aerobic exercise intervention. Specifically, changes in myosin heavy chain isoform distribution, muscle mass and myofiber cross sectional area were studied in response to sedentary behaviour and to a 5-week aerobic exercise intervention. Mice (n=24) were assigned to either remain sedentary (SED, n=24), or assigned to a 4-week exercise training program (EXT, n=24) and further spit into their final groupings with sedentary control (SED+C) and exercise control (EXT+C) groups receiving saline injections and sedentary sclerostin (SED+S) and exercise sclerostin (EXT+S) groups recombinant sclerostin. Soleus and extensor digitorum longus muscle were then extracted and analyzed via fluorescent immunohistochemistry and Western blotting. Sclerostin injection led to a significant reduction in soleus MHCI, MHC1/IIA, MHCIIA/X and MHC IIB cross-sectional area (p < .5) along with trending declines in MHC IIA (p = .1). In contrast to this, there was no effect of sclerostin injection on MHC IIX or MHCIIXB CSA. In EDL tissue there was a trend towards a decrease in tissue necropsy weight in the sclerostin injection group (p = .1). Sclerostin appeared to have no effect on total MHC protein content or in the examined markers of Wnt signaling (GSK3β, β-catenin) as detected in both soleus and EDL muscle tissue via western blot. Our findings demonstrate that sclerostin negatively influences muscle tissue via decreases in myofibril cross-sectional area and these decreases trend towards a significant reduction in muscle mass