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Iskalni niz: "avtor" (Carlo Reggiani) .

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Irisin attenuates muscle impairment during bed rest through muscle-adipose tissue crosstalk
Andrea D'Amuri, Juana Maria Sanz, Stefano Lazzer, Rado Pišot, Boštjan Šimunič, Gianni Biolo, Giovanni Zuliani, Mladen Gasparini, Marco Vincenzo Narici, Bruno Grassi, Carlo Reggiani, Edoardo Dalla Nora, Angelina Passaro, 2022, izvirni znanstveni članek

Povzetek: Simple Summary: Irisin is a known myokine secreted mainly by the muscle that is produced after physical activity. It induces browning in the adipose tissue with a consequent increase in mitochondrial oxidation of lipids and reduction of insulin resistance; thus, it has been hypothesized that irisin was the molecule mediating most of the beneficial effects related to exercise on adipose tissue and consequently on the whole organism. In our study we observed that extreme physical inactivity induces the loss of muscle mass and function, and an increase in the body adipose tissue as expected. However, of note, circulating irisin levels were increased secondary to enhanced irisin synthesis mainly from adipose tissue rather than muscle. In addition, subjects who produced more irisin had reduced muscle impairment. Therefore, our hypothesis is that there is negative feedback within the muscle-adipose tissue crosstalk, specifically not only does the muscle influence the adipose tissue through irisin during exercise, but also the adipose tissue protects the muscle during inactivity.Abstract: The detrimental effect of physical inactivity on muscle characteristics are well known. Irisin, an exercise-induced myokine cleaved from membrane protein fibronectin type III domain-containing protein-5 (FNDC5), mediates at least partially the metabolic benefits of exercise. This study aimed to assess the interplay between prolonged inactivity, circulating irisin, muscle performance, muscle fibers characteristics, as well as the FNDC5 gene expression (FNDC5ge) in muscle and adipose tissue among healthy subjects. Twenty-three healthy volunteers were tested before and after 14 days of Bed Rest, (BR). Post-BR circulating levels of irisin significantly increased, whereas body composition, muscle performance, and muscle fiber characteristics deteriorated. Among the subjects achieving the highest post-BR increase of irisin, the lowest reduction in maximal voluntary contraction and specific force of Fiber Slow/1, the highest increase of FNDC5ge in adipose tissue, and no variation of FNDC5ge in skeletal muscle were recorded. Subjects who had the highest FNDC5ge in adipose tissue but not in muscle tissue showed the highest circulating irisin levels and could better withstand the harmful effect of BR.
Ključne besede: physical inactivity, bed rest, FNDC5 gene expression, myokines, sarcopenia, muscles fiber
Objavljeno v DiRROS: 07.07.2022; Ogledov: 91; Prenosov: 57
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Neuromuscular junction instability and altered intracellular calcium handling as early determinants of force loss during unloading in humans
Elena Monti, Carlo Reggiani, Martino V. Franchi, Luana Toniolo, Marco Sandri, Andrea Armani, Sandra Zampieri, Boštjan Šimunič, Rado Pišot, Marco Vincenzo Narici, 2021, izvirni znanstveni članek

Povzetek: Unloading induces rapid skeletal muscle atrophy and functional decline. Importantly, force is lost at a much higher rate than muscle mass. We aimed to investigate the early determinants of the disproportionate loss of force compared to that of muscle mass in response to unloading. Ten young participants underwent 10 days of bed rest (BR). At baseline (BR0) and at 10 days (BR10), quadriceps femoris (QF) volume (VOL) and isometric maximum voluntary contraction (MVC) were assessed. At BR0 and BR10 blood samples and biopsies of vastus lateralis (VL) muscle were collected. Neuromuscular junction (NMJ) stability and myofibre innervation status were assessed, together with single fibre mechanical properties and sarcoplasmic reticulum (SR) calcium handling. From BR0 to BR10, QFVOL and MVC decreased by 5.2% (P = 0.003) and 14.3% (P < 0.001), respectively. Initial and partial denervation was detected from increased neural cell adhesion molecule (NCAM)-positive myofibres at BR10 compared with BR0 (+3.4%, P = 0.016). NMJ instability was further inferred from increased C-terminal agrin fragment concentration in serum (+19.2% at BR10, P = 0.031). Fast fibre cross-sectional area (CSA) showed a trend to decrease by 15% (P = 0.055) at BR10, while single fibre maximal tension (force/CSA) was unchanged. However, at BR10 SR Ca2+ release in response to caffeine decreased by 35.1% (P < 0.002) and 30.2% (P < 0.001) in fast and slow fibres, respectively, pointing to an impaired excitation%contraction coupling. These findings support the view that the early onset of NMJ instability and impairment in SR function are eligible mechanisms contributing to the greater decline in muscle force than in muscle size during unloading.
Ključne besede: Ca2+ dynamics, muscle atrophy, neuromuscular junction instability, sarcoplasmic reticulum, single fibre atrophy, single fibre contractile impairment, unloading
Objavljeno v DiRROS: 16.06.2021; Ogledov: 549; Prenosov: 525
.pdf Celotno besedilo (3,39 MB)
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