1. Alterations in Muscle Contractile Properties, Structure, and Function During 10-Day Bed Rest, Post-Recovery, and Following COVID-19 LockdownBoštjan Šimunič, Martino V. Franchi, Fabio Sarto, Elena Monti, zaključena znanstvena zbirka raziskovalnih podatkov Povzetek: We aimed to identify early tensiomyography alterations in six muscles during a 10-day bed rest (BR10), followed by a 30-day recovery period (R+30), and to compare these changes with those observed after the 54-day COVID-19 lockdown in ten healthy males (22.9 ± 5.0 years). Tensiomyography and muscle thickness (sonography) were assessed at baseline, during bed rest, at BR10, R+30, and after the COVID-19 lockdown. Additional assessments included vertical jump performance (force plate), body composition (bioimpedance), physical activity (GPAQ), and lower back pain (VAS). By BR10, participants experienced a 1.9% body mass loss, a 3.8% increase in fat mass, and a 2.4% reduction in muscle mass. While anthropometric parameters returned to baseline by R+30, fat mass increased again by 3.9% post-lockdown. Jump height declined by 10.1% at BR10, returned to baseline at R+30, and remained stable thereafter. Muscle thickness decreased by 7.0% in the vastus lateralis at BR10 and by 10.1% post-lockdown. Tensiomyographic amplitude increased in all five leg muscles prior to BR10, recovered at R+30 and increased again after the COVID-19 lockdown, while a reduction was observed in the erector spinae within the first 48 hours, coinciding with reported lower back pain. In the erector spinae, both delay and contraction time decreased during BR10 and post-lockdown. In contrast, contraction time of the biceps femoris increased before BR10 and remained elevated post-lockdown. Overall, tensiomyographic parameters after the COVID-19 lockdown changed in the same direction as during bed rest, though to a lesser degree, make it a sensitive tool for detecting changes in muscle structural and functional quality after bed rest and reduced activity paradigms.
Ključne besede: Atrophy, Bed rest, Physical inactivity, Skeletal muscle, Tensiomyography
Objavljeno v DiRROS: 25.06.2025; Ogledov: 396; Prenosov: 0
 Celotno besedilo (251,56 KB) |
2. Mitochondrial sensitivity to submaximal [ADP] following bed rest : a novel two-phase approach associated with fibre typesLucrezia Zuccarelli, Maria De Martino, Antonio Filippi, Alice E. Knapton, Benjamin D. Thackray, Giovanni Baldassarre, Boštjan Šimunič, Rado Pišot, Giuseppe Sirago, Elena Monti, Marco Vincenzo Narici, Miriam Isola, Andrew J. Murray, Giovanna Lippe, Bruno Grassi, 2025, izvirni znanstveni članek Povzetek: Background: We recently demonstrated that following a 10-day exposure to inactivity/simulated microgravity impairments ofoxidative metabolism were located ‘upstream’ of mitochondrial function, as evaluated by maximal ADP-stimulated mitochon-drial respiration (JO 2max) determined ex vivo. The aim of this study was to evaluate mitochondrial sensitivity to submaximal[ADP] by an alternative approach aimed at identifying responses associated with fibre type composition.Methods: Isolated permeabilized vastus lateralis fibres were analysed by high-resolution respirometry in 9 young males beforeand after a 10-day horizontal bed rest. Eleven submaximal titrations of ADP (from 12.5 to 10 000 μM) were utilized to assess com-plex I + II-linked ADP sensitivity. We applied to JO 2 versus [ADP] data a traditional Michaelis–Menten kinetics equation, withthe calculation of the apparent K m and maximal respiration (Vmax), and two ‘sequential’ hyperbolic equations, yielding two K mand Vmax values. The two-hyperbolic equations were solved and the [ADP] value corresponding to 50% of JO 2max was calculated.Isoform expression of myosin heavy chains (MyHC) 1, 2A and 2X was also determined. Control experiments were also carriedout on rat skeletal muscle samples with different percentages of MyHC isoforms.Results: The two hyperbolic equations provided an alternative fitting of data and identified two distinct phases of the JO 2 versus[ADP] response: a first phase characterized by low Vmax (Vmax1 , 28 ± 10 pmol s−1 mg−1) and apparent K m (K m1 , 62 ± 54 μM) anda second phase characterized by higher Vmax (Vmax2 , 61 ± 16 pmol s−1 mg−1) and K m (K m2 , 1784 ± 833 μM). Data were confirmedin control experiments carried out in rat muscle samples with different percentages of MyHC isoforms. Correlation and receiveroperating characteristics analyses suggest that the two phases of the response were related to the % of MyHC isoforms.Conclusions: A novel mathematical approach (two sequential hyperbolic functions) for the fitting of JO 2 versus [ADP] data ob-tained by high-resolution respirometry on permeabilized skeletal muscle fibres, obtained in humans and rats, provided an alter-native fitting of the experimental data compared to the traditional Michaelis–Menten kinetics equation. This alternative modelallowed the identification of two distinct phases in the responses, which were related to fibre type composition. A first phase, characterized by low apparent K m and Vmax values, was correlated with the percentage of less oxidative (Type 2A + 2X) MyHCisoforms. A second phase, characterized by high apparent K m and Vmax , was related to more oxidative (Type 1) MyHC isoforms.
Ključne besede: ADP, bed rest, mitochondrial sensitivity, myosin heavy chains, skeletal muscle mitochondria
Objavljeno v DiRROS: 05.05.2025; Ogledov: 518; Prenosov: 295
Celotno besedilo (3,59 MB)
Gradivo ima več datotek! Več... |
3. Mitochondria can substitute for parvalbumin to lowercytosolic calcium levels in the murine fast skeletal muscleLorenzo Marcucci, Leonardo Nogara, Marta Canato, Elena Germinario, Anna Raffaello, Michela Carraro, Paolo Bernardi, Laura Pietrangelo, Simona Boncompagni, Feliciano Protasi, Nazareno Paolocci, Carlo Reggiani, 2024, izvirni znanstveni članek Povzetek: Aim: Parvalbumin (PV) is a primary calcium buffer in mouse fast skeletal musclefibers. Previous work showed that PV ablation has a limited impact on cytosolicCa2+ ([Ca2+]cyto) transients and contractile response, while it enhances mitochon-drial density and mitochondrial matrix-free calcium concentration ([Ca2+]mito).Here, we aimed to quantitatively test the hypothesis that mitochondria act tocompensate for PV deficiency.Methods: We determined the free Ca 2+ redistribution during a 2 s 60 Hz tetanicstimulation in the sarcoplasmic reticulum, cytosol, and mitochondria. Via a re-action–diffusion Ca 2+ model, we quantitatively evaluated mitochondrial uptakeand storage capacity requirements to compensate for PV lack and analyzed pos-sible extracellular export.Results: [Ca 2+]mito during tetanic stimulation is greater in knock-out (KO)(1362 ± 392 nM) than in wild-type (WT) (855 ± 392 nM), p < 0.05. Under the as-sumption of a non-linear intramitochondrial buffering, the model predicts an ac-cumulation of 725 μmoles/Lfiber (buffering ratio 1:11 000) in KO, much higherthan in WT (137 μmoles/Lfiber, ratio 1:4500). The required transport rate via mi-tochondrial calcium uniporter (MCU) reaches 3 mM/s, compatible with availableliterature. TEM images of calcium entry units and Mn2+ quenching showed a greater capacity of store- operated calcium entry in KO compared to WT. However,levels of [Ca 2+]cyto during tetanic stimulation were not modulated to variations ofextracellular calcium.Conclusions: The model-based analysis of experimentally determined calciumdistribution during tetanic stimulation showed that mitochondria can act as abuffer to compensate for the lack of PV. This result contributes to a better under-standing of mitochondria's role in modulating [Ca2+]cyto in skeletal muscle fibers.
Ključne besede: calcium, mitochondria, mouse skeletal muscle fibers, parvalbumin, reaction-diffusion model
Objavljeno v DiRROS: 13.11.2024; Ogledov: 637; Prenosov: 3218
Celotno besedilo (3,97 MB)
Gradivo ima več datotek! Več... |
4. Spaceflight on the ISS changed the skeletal muscle proteome of two astronautsMarta Murgia, Joern Rittweger, Carlo Reggiani, Roberto Bottinelli, Matthias Mann, Stefano Schiaffino, Marco Vincenzo Narici, 2024, izvirni znanstveni članek Povzetek: Skeletal muscle undergoes atrophy and loss of force during long space missions, when astronauts are persistently exposed to altered gravity and increased ionizing radiation. We previously carried out mass spectrometry-based proteomics from skeletal muscle biopsies of two astronauts, taken before and after a mission on the International Space Station. The experiments were part of an effort to find similarities between spaceflight and bed rest, a ground-based model of unloading, focused on proteins located at the costameres. We here extend the data analysis of the astronaut dataset and show compartment-resolved changes in the mitochondrial proteome, remodeling of the extracellular matrix and of the antioxidant response. The astronauts differed in their level of onboard physical exercise, which correlated with their respective preservation of muscle mass and force at landing in previous analyses. We show that the mitochondrial proteome downregulation during spaceflight, particularly the inner membrane and matrix, was dramatic for both astronauts. The expression of autophagy regulators and reactive oxygen species scavengers, however, showed partially opposite expression trends in the two subjects, possibly correlating with their level of onboard exercise. As mitochondria are primarily affected in many different tissues during spaceflight, we hypothesize that reactive oxygen species (ROS) rather than mechanical unloading per se could be the primary cause of skeletal muscle mitochondrial damage in space. Onboard physical exercise might have a strong direct effect on the prevention of muscle atrophy through mechanotransduction and a subsidiary effect on mitochondrial quality control, possibly through upregulation of autophagy and anti-oxidant responses.
Ključne besede: skeletal muscles, microgravity, muscle atrophy, autophagy
Objavljeno v DiRROS: 12.11.2024; Ogledov: 698; Prenosov: 602
Celotno besedilo (1,55 MB)
Gradivo ima več datotek! Več... |
5. |
6. Radiological assessment of skeletal muscle index and myosteatosis and their impact postoperative outcomes after liver transplantationMiha Petrič, Taja Jordan, Karteek Popuri, Sabina Ličen, Blaž Trotovšek, Aleš Tomažič, 2023, izvirni znanstveni članek Povzetek: Background. Liver transplantation offers curative treatment to patients with acute and chronic end-stage liver disease. The impact of nutritional status on postoperative outcomes after liver transplantation remains poorly under-stood. The present study investigated the predictive value of radiologically assessed skeletal muscle index (SMI) and myosteatosis (MI) on postoperative outcomes.Patients and methods. Data of 138 adult patients who underwent their first orthotopic liver transplantation were retrospectively analysed. SMI and MI in computer tomography (CT) scan at the third lumbar vertebra level were cal-culated. Results were analyzed for the length of hospitalisation and postoperative outcomes.Results. In 63% of male and 28.9% of female recipients, low SMI was found. High MI was found in 45(32.6%) patients. Male patients with high SMI had longer intensive care unit (ICU) stay (P < 0.025). Low SMI had no influence on ICU stay in female patients (P = 0.544), length of hospitalisation (male, P > 0.05; female, P = 0.843), postoperative complication rates (males, P = 0.883; females, P = 0.113), infection rate (males, P = 0.293, females, P = 0.285) and graft rejection (males, P = 0.875; females, P = 0.135). The presence of MI did not influence ICU stay (P = 0.161), hospitalization (P = 0.771), postoperative complication rates (P = 0.467), infection rate (P = 0.173) or graft rejection rate (P = 0.173).Conclusions. In our study, changes in body composition of liver transplant recipients observed with SMI and MI had no impact on postoperative course after liver transplantation. CT body composition analysis of recipients and uni-formly accepted cut-off points are crucial to producing reliable data in the future.
Ključne besede: muscle mass, liver transplantation, myosteatosis, skeletal muscle index, GLIM score
Objavljeno v DiRROS: 25.07.2024; Ogledov: 856; Prenosov: 770
Celotno besedilo (1,69 MB)
Gradivo ima več datotek! Več... |
7. Neuromuscular component of muscle quality assessment in older adults : narrative reviewKatarina Puš, Boštjan Šimunič, 2024, pregledni znanstveni članek Povzetek: The concept of muscle quality encompasses both microand macroscopic aspects of muscle architecture and composition and has gained increasing attention with inclusion in the definition of sarcopenia, indicating the significance of muscle quality in evaluating muscle function and strength among older individuals. Muscle quality consists of two main components: neuromuscular and morphological and is often defined as the ratio between the two. The aim of this review is to present currently used methods for assessment of muscle quality with an emphasis on neuromuscular component in older adults. The most used methods for assessing morphological component are imaging techniques, such as magnetic resonance imaging, computed tomography, dualenergy X-ray absorptiometry and non-imaging bioimpedance analysis. In the neuromuscular component upper and lower body strength are assessed with different methods such as hand grip strength, isokinetic lower limb strength and isometric lower limb strength. Currently, there are three proposed muscle quality assessment methods for field or population studies: muscle quality index, ultrasound sarcopenia index and bioimpedancederived phase angle. Despite the exploration of muscle quality through various assessment methods, a consensus on the most appropriate and universally applicable approach has yet to be established.
Ključne besede: ageing, skeletal muscle, ultrasound sarcopenia index, muscle quality index, phase angle
Objavljeno v DiRROS: 13.05.2024; Ogledov: 1023; Prenosov: 574
Celotno besedilo (347,88 KB)
Gradivo ima več datotek! Več... |
8. Red blood cell transfusion and skeletal muscle tissue oxygenation in anaemic haematologic outpatientsMatej Podbregar, Ana Uršula Gavrič, Eva Podbregar, Hugon Možina, Sebastian Stefanović, 2016, izvirni znanstveni članek Povzetek: Background. Stored red blood cells (RBCs) accumulate biochemical and biophysical changes, known as storage lesion. The aim of this study was to re-challenge current data that anaemia in chronically anaemic haematology patients is not associated with low skeletal muscle tissue oxygen (StO2), and that RBC storage age does not influence the tissue response after ischaemic provocation, using near-infrared spectroscopy. Patients and methods. Twenty-four chronic anaemic haematology patients were included. Thenar skeletal muscle StO2 was measured at rest (basal StO2), with vascular occlusion testing (upslope StO2, maximum StO2) before and after transfusion. Results. Basal StO2 was low (53% +- 7%). Average RBC storage time was 10.5 +- 3.9 days. Effects of RBC transfusions were as follows: basal StO2 and upslope StO2 did not change significantly; maximum StO2 increased compared to baseline (64 +- 14% vs. 59 +- 10%, p = 0.049). Change of basal StO2, upslope StO2 and maximum StO2 was negatively related to age of RBCs. The decrease of maximum StO2 was predicted (sensitivity 70%, specificity 100%), after receiving RBCs >- 10days old. Discussion. Resting skeletal muscle StO2 in chronic anaemic patients is low. RBC storage time affects skeletal muscle StO2 in the resting period and after ischaemic provocation.
Ključne besede: skeletal muscle, transfusion, red blood cells
Objavljeno v DiRROS: 09.05.2024; Ogledov: 915; Prenosov: 544
Celotno besedilo (958,31 KB)
Gradivo ima več datotek! Več... |
9. Exploration of macromolecular phenotype of human skeletal muscle in diabetes using infrared spectroscopyBarbara Zupančič, Chiedozie Kenneth Ugwoke, Mohamed Elwy Abdelmonaem, Armin Alibegović, Erika Cvetko, Jože Grdadolnik, Anja Šerbec, Nejc Umek, 2023, izvirni znanstveni članek Povzetek: Introduction: The global burden of diabetes mellitus is escalating, and more efficient investigative strategies are needed for a deeper understanding of underlying pathophysiological mechanisms. The crucial role of skeletal muscle in carbohydrate and lipid metabolism makes it one of the most susceptible tissues to diabetes-related metabolic disorders. In tissue studies, conventional histochemical methods have several technical limitations and have been shown to inadequately characterise the biomolecular phenotype of skeletal muscle to provide a holistic view of the pathologically altered proportions of macromolecular constituents. Materials and methods: In this pilot study, we examined the composition of five different human skeletal muscles from male donors diagnosed with type 2 diabetes and non-diabetic controls. We analysed the lipid, glycogen, and collagen content in the muscles in a traditional manner with histochemical assays using different staining techniques. This served as a reference for comparison with the unconventional analysis of tissue composition using Fourier-transform infrared spectroscopy as an alternative methodological approach. Results: A thorough chemometric post-processing of the infrared spectra using a multi-stage spectral decomposition allowed the simultaneous identification of various compositional details from a vibrational spectrum measured in a single experiment. We obtained multifaceted information about the proportions of the different macromolecular constituents of skeletal muscle, which even allowed us to distinguish protein constituents with different structural properties. The most important methodological steps for a comprehensive insight into muscle composition have thus been set and parameters identified that can be used for the comparison between healthy and diabetic muscles. Conclusion: We have established a methodological framework based on vibrational spectroscopy for the detailed macromolecular analysis of human skeletal muscle that can effectively complement or may even serve as an alternative to histochemical assays. As this is a pilot study with relatively small sample sets, we remain cautious at this stage in drawing definitive conclusions about diabetes-related changes in skeletal muscle composition. However, the main focus and contribution of our work has been to provide an alternative, simple and efficient approach for this purpose. We are confident that we have achieved this goal and have brought our methodology to a level from which it can be successfully transferred to a large-scale study that allows the effects of diabetes on skeletal muscle composition and the interrelationships between the macromolecular tissue alterations due to diabetes to be investigated.
Ključne besede: diabetes mellitus, skeletal muscle, metabolism, macromulecular composition, infrared spectroscopy, multivariate analysis, histochemical assays
Objavljeno v DiRROS: 11.01.2024; Ogledov: 1503; Prenosov: 654
Celotno besedilo (1,71 MB)
Gradivo ima več datotek! Več... |
10. |
