Publications by authors named "Luana Toniolo"

46 Publications

Neuromuscular junction instability and altered intracellular calcium handling as early determinants of force loss during unloading in humans.

J Physiol 2021 Jun 19;599(12):3037-3061. Epub 2021 May 19.

Department of Biomedical Sciences, University of Padova, Padova, 35131, Italy.

Key Points: Few days of unloading are sufficient to induce a decline of skeletal muscle mass and function; notably, contractile force is lost at a faster rate than muscle mass. The reasons behind this disproportionate loss of muscle force are still poorly understood. We provide strong evidence of two mechanisms only hypothesized until now for the rapid muscle force loss in only 10 days of bed rest. Our results show that an initial neuromuscular junction instability, accompanied by alterations in the innervation status and impairment of single fibre sarcoplasmic reticulum function contribute to the loss of contractile force in front of a preserved myofibrillar function and central activation capacity. Early onset of neuromuscular junction instability and impairment in calcium dynamics involved in excitation-contraction coupling are proposed as eligible determinants to the greater decline in muscle force than in muscle size during unloading.

Abstract: 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 Ca 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.
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http://dx.doi.org/10.1113/JP281365DOI Listing
June 2021

Are muscle fibres of body builders intrinsically weaker? A comparison with single fibres of aged-matched controls.

Acta Physiol (Oxf) 2021 02 20;231(2):e13557. Epub 2020 Sep 20.

Department of Biomedical Sciences, University of Padova, Padova, Italy.

Aim: Skeletal muscles of Body Builders (BB) represent an interesting model to study muscle mass gains in response to high volume resistance training. It is debated whether muscle contractile performance improves in proportion to mass. Here, we aim to assess whether muscle hypertrophy does not occur at the expense of performance.

Methods: Six BB and Six untrained controls (CTRL) were recruited. Cross-sectional area (CSA) and maximum voluntary contraction (MVC) of quadriceps femoris muscle (QF) and CSA and architecture of vastus lateralis (VL) were determined. Moreover, a biopsy was taken from VL mid-portion and single fibres were analysed.

Results: QF CSA and MVC were 32% (n.s., P = .052) and 58% (P = .009) higher in BB than in CTRL, respectively. VL CSA was 37% higher in BB (P = .030). Fast 2A fibres CSA was 24% (P = .048) greater in BB than in CTRL, when determined in immunostained sections of biopsy samples. Single permeabilized fast fibres CSA was 37% (n.s., P = .052) higher in BB than in CTRL, and their force was slightly higher in BB (n.s.), while specific tension (P ) was 19% (P = .024) lower. The lower P was not explained either by lower myosin content or by impaired calcium diffusion. Conversely, the swelling caused by skinning-induced permeabilization was different and, when used to correct P , differences between populations disappeared.

Conclusions: The results show that high degree of muscle hypertrophy is not detrimental for force generation capacity, as increases in fibre size and force are strictly proportional once the differential swelling response is accounted for.
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http://dx.doi.org/10.1111/apha.13557DOI Listing
February 2021

Age Dependent Modification of the Metabolic Profile of the Tibialis Anterior Muscle Fibers in C57BL/6J Mice.

Int J Mol Sci 2020 May 30;21(11). Epub 2020 May 30.

Laboratory of Muscle Biophysics, Department of Biomedical Sciences, University of Padova, 35131 Padova, Italy.

Skeletal muscle aging is accompanied by mass reduction and functional decline, as a result of multiple factors, such as protein expression, morphology of organelles, metabolic equilibria, and neural communication. Skeletal muscles are formed by multiple fibers that express different Myosin Heavy Chains (MyHCs) and have different metabolic properties and different blood supply, with the purpose to adapt their contraction to the functional need. The fine interplay between the different fibers composing a muscle and its architectural organization determine its functional properties. Immunohistochemical and histochemical analyses of the skeletal muscle tissue, besides evidencing morphological characteristics, allow for the precise determination of protein expression and metabolic properties, providing essential information at the single-fiber level. Aiming to gain further knowledge on the influence of aging on skeletal muscles, we investigated the expression of the MyHCs, the Succinate Dehydrogenase (SDH) activity, and the presence of capillaries and Tubular Aggregates (TAs) in the tibialis anterior muscles of physiologically aging C57BL/6J mice aged 8 (adult), 18 (middle aged), and 24 months (old). We observed an increase of type-IIB fast-contracting fibers, an increase of the oxidative capacity of type-IIX and -IIA fibers, a general decrease of the capillarization, and the onset of TAs in type-IIB fibers. These data suggest that aging entails a selective modification of the muscle fiber profiles.
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http://dx.doi.org/10.3390/ijms21113923DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7312486PMC
May 2020

Long-term resveratrol treatment improves the capillarization in the skeletal muscles of ageing C57BL/6J mice.

Int J Food Sci Nutr 2021 Feb 24;72(1):37-44. Epub 2020 May 24.

Department of Medicine, Surgery and Health Sciences, University of Trieste, Trieste, Italy.

We recently showed that the treatment with Resveratrol (RES) contrasts the effects of ageing on the skeletal muscle (SKM), reduces the appearance of tubular aggregates (TAs), and improves the fatigue resistance. Since fatigue resistance depends on the SKM capillary network, and RES has been described to improve vascularisation, we analysed the SKM capillarization in naturally ageing C57BL/6J male mice, fed with 0.04% RES in the diet for 6 months, which showed a better fatigue resistance in a previous work. Our data show an inverse correlation between the number of capillaries per fibre (CAF) and TAs in both control and treated type IIB fibres, and an increase of CAF in ageing SKM upon RES-treatment. The present work suggests that capillarization is one of the determinants of the development of TAs and fatigue resistance, and that RES can be considered a good candidate to counteract capillary rarefaction in the SKM tissue.
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http://dx.doi.org/10.1080/09637486.2020.1769569DOI Listing
February 2021

Corrigendum: Skeletal Muscle Fiber Size and Gene Expression in the Oldest-Old With Differing Degrees of Mobility.

Front Physiol 2020;11:127. Epub 2020 Feb 25.

Department of Biomedical Sciences, University of Padova, Padua, Italy.

[This corrects the article DOI: 10.3389/fphys.2019.00313.].
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http://dx.doi.org/10.3389/fphys.2020.00127DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7052352PMC
February 2020

Musculoskeletal adaptations to strength training in frail elderly: a matter of quantity or quality?

J Cachexia Sarcopenia Muscle 2020 06 24;11(3):663-677. Epub 2020 Feb 24.

Department of Physical Performance, Norwegian School of Sport Sciences, Sognsveien, Oslo, Norway.

Background: The improvement in muscle strength generally exceeds the increase in muscle size following strength training in frail elderly, highlighting the complex aetiology of strength deficit in aging. The aim of this study was to investigate the effect of heavy-load strength training on a broad number of factors related to specific strength in frail elderly.

Methods: Thirty-four frail elderly men (n = 18) and women (n = 16) aged 67 to 98 (86 ± 7 years) were randomized to either a group performing strength training twice a week for 10 weeks (ST) or a non-exercising control group (CON). Knee extensor muscle strength was tested as one-repetition maximum (1RM) and isometric maximal voluntary contraction (MVC) torque. Muscle activation was assessed by the interpolated twitch technique, and muscle density [mean Hounsfield units (HU)] and intermuscular adipose tissue (IMAT) by computed tomography scans of the quadriceps femoris. Muscle biopsies from the vastus lateralis were obtained to investigate changes in intramyocellular lipids and single-fibre specific tension.

Results: In ST, knee extension 1RM and MVC improved by 17 and 7%, respectively. Muscle cross-sectional area of the quadriceps femoris increased by 7%, accompanied by a 4% increase of muscle density. No changes in IMAT, voluntary activation level, single-fibre specific tension, or lipid content were observed.

Conclusions: In contrast to several previous reports, the improvements in isometric muscle strength and muscle area were in good agreement in the present study. The training-induced increase in muscle density was not due to changes in skeletal muscle lipid content. Instead, the increase in muscle density may reflect increased packing of contractile material or simply an increased ratio of muscle tissue relative to IMAT.
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http://dx.doi.org/10.1002/jcsm.12543DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7296272PMC
June 2020

Neuromuscular Electrical Stimulation Induces Skeletal Muscle Fiber Remodeling and Specific Gene Expression Profile in Healthy Elderly.

Front Physiol 2019 27;10:1459. Epub 2019 Nov 27.

Department of Neuroscience Imaging and Clinical Sciences, 'G. d'Annunzio' University of Chieti-Pescara, Chieti, Italy.

Skeletal muscle aging is a multifactorial process strictly related to progressive weakness. One of the results that were focused on was the fiber phenotype modification and their loss. The physiological muscle recruitment to contraction, basically prosecuted under volitional control, can also be engaged by means of Neuromuscular Electrical Stimulation (NMES). Knowing that the NMES is effective in improving muscle strength in active healthy elderly, the aim was to investigate which physiological modifications were able to produce in the muscle and the pathways involved. It was found that NMES increased the cross sectional area and the isometric strength of type II myofibers together with the activated myogenic pathway in order to shift glycolytic toward the oxidative phenotype II myofibers, at a molecular level and with an increase of maximal voluntary contraction (MVC) at a functional level. Using the TaqMan low density array on 48 different genes, we found that NMES specific gene regulation highlighted: (i) increased protein synthesis with respect to protein degradation; (ii) the activation of an apoptotic pathway involved in the differentiation process; (iii) increased regeneration signals; (iv) oxidative enzyme regulation. These pathways were validated via confirmatory RT-PCR for genes involved in the regeneration process as well as Myosin isoforms. We also investigated the oxidative stress status analyzing superoxide anion levels, the protein expression of two different superoxide dismutase and the activity of both catalase and superoxide anion dismutase, being two main antioxidant enzymes. In conclusion, data demonstrates that NMES is effective in producing physiological adaptation on of active healthy elderly as well as providing new insights for further research on elderly who experienced muscle detriment for periodic or permanent immobility.
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http://dx.doi.org/10.3389/fphys.2019.01459DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6890722PMC
November 2019

Age-dependent variations in the expression of myosin isoforms and myogenic factors during the involution of the proximal sesamoidean ligament of sheep.

Res Vet Sci 2019 Jun 11;124:270-279. Epub 2019 Apr 11.

Department of Comparative Biomedicine and Food Science, Università di Padova, Italy. Electronic address:

In ungulates the stability of the fetlock joint is dependent on several muscles, which are exposed to high stress and strain. Among those muscles, the proximal sesamoidean ligament or PSL (also known as the suspensory ligament or Ruini's elasto-tendinous organ) is organized at birth in layers of muscle fibres alternated with abundant tendinous tissue that, during the postnatal development, becomes the predominant tissue. In this study we analysed the PSL of the sheep at the age of 1, 30 and 180 days and determined the expression of several genes which either (a) are markers of muscle fibre growth and maturation, or (b) play a role as signal molecules. We observed an accelerated maturation, as indicated by the transition of MyHC isoform expression towards the slow isoforms and a reduced regenerative potential indicated by the low Pax7 expression and the altered Wnt signalling. We also found a specific myogenic expression pattern of MyoD, Myf5 and Myogenin in the developing PSL and high mRNA levels of specific fibrogenic factors, as TGF-β1, that, undoubtedly, stimulate the growth of connective tissue. Our observations confirmed, at molecular level, the peculiarity of the fast involution observed in PSL a muscle that undergoes a very specific active differentiation process during early development, which implies myofibres involution and their replacement with connective tissue.
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http://dx.doi.org/10.1016/j.rvsc.2019.04.006DOI Listing
June 2019

Skeletal Muscle Fiber Size and Gene Expression in the Oldest-Old With Differing Degrees of Mobility.

Front Physiol 2019 26;10:313. Epub 2019 Mar 26.

Department of Biomedical Sciences, University of Padova, Padua, Italy.

The oldest-old, in the ninth and tenth decades of their life, represent a population characterized by neuromuscular impairment, which often implies a loss of mobility and independence. As recently documented by us and others, muscle atrophy and weakness are accompanied by an unexpected preservation of the size and contractile function of skeletal muscle fibers. This suggests that, while most fibers are likely lost with their respective motoneurons, the surviving fibers are well preserved. Here, we investigated the mechanisms behind this fiber preservation and the relevance of physical activity, by comparing a group of 6 young healthy controls (YG: 22-28 years) with two groups of oldest-old (81-96 years), one able to walk (OW: = 6, average 86 years) and one confined to a wheelchair (ONW = 9, average 88 years). We confirmed previous results of fiber preservation and, additionally, observed a shift in fiber type, toward slow predominance in OW and fast predominance in ONW. Myonuclear density was increased in muscles of ONW, compared to YG and OW, potentially indicative of an ongoing atrophy process. We analyzed, by RT-qPCR, the expression of genes relevant for fiber size and type regulation in a biopsy sample from the vastus lateralis. In all oldest-old both myostatin and IGF-1 expression were attenuated compared to YG, however, in ONW two specific IGF-1 isoforms, IGF-1EA and MGF, demonstrated a further significant decrease compared to OW. Surprisingly, atrogenes (MURF1 and atrogin) expression was also significantly reduced compared to YG and this was accompanied by a close to statistically significantly attenuated marker of autophagy, LC3. Among the determinants of the metabolic fiber type, PGC1α was significantly reduced in both OW and ONW compared to YG, while AMPK was down-regulated only in ONW. We conclude that, in contrast to the shift of the balance in favor of pro-atrophy factors found by other studies in older adults (decreased IGF-1, increase of myostatin, increase of atrogenes), in the oldest-old the pro-atrophy factors also appear to be down-regulated, allowing a partial recovery of the proteostasis balance. Furthermore, the impact of muscle activity, as a consequence of lost or preserved walking ability, is limited.
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http://dx.doi.org/10.3389/fphys.2019.00313DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6443969PMC
March 2019

Resveratrol treatment reduces the appearance of tubular aggregates and improves the resistance to fatigue in aging mice skeletal muscles.

Exp Gerontol 2018 10 20;111:170-179. Epub 2018 Jul 20.

Department of Molecular and Developmental Medicine, University of Siena, Italy; Interuniversity Institute of Myology, Italy. Electronic address:

Resveratrol (RES) is a polyphenolic compound found in grapes, peanuts, and in some berries. RES has been reported to exhibit antioxidant, anti-inflammatory, anti-proliferative properties, and to target mitochondrial-related pathways in mammalian cells and animal models. Therefore, RES is currently advised as supplement in the diet of elderly individuals. Although it is hypothesized that some of RES beneficial actions likely arise from its action on the skeletal muscle, the investigation of RES effects on this tissue remains still elusive. This study reports the effects of a 0,04% RES-supplemented diet for six months, on the skeletal muscle properties of C57/BL6 aging mice. The analysis of the morphology, protein expression, and functional-mechanical properties of selected skeletal muscles in treated compared to control mice, revealed that treated animals presented less tubular aggregates and a better resistance to fatigue in an ex-vivo contraction test, suggesting RES as a good candidate to reduce age-related alterations in muscle.
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http://dx.doi.org/10.1016/j.exger.2018.07.012DOI Listing
October 2018

Loss of maximal explosive power of lower limbs after 2 weeks of disuse and incomplete recovery after retraining in older adults.

J Physiol 2018 02 19;596(4):647-665. Epub 2018 Jan 19.

Department of Medicine, University of Udine, Udine, Italy.

Key Points: Disuse in older adults can critically decrease lower limb muscle power, leading to compromised mobility and overall quality of life. We studied how muscle power and its determinants (muscle mass, single muscle fibre properties and motor control) adapted to 2 weeks of disuse and subsequent 2 weeks of physical training in young and older people. Disuse decreased lower limb muscle power in both groups; however, different adaptations in single muscle fibre properties and co-contraction of leg muscles were observed between young and older individuals. Six physical training sessions performed after disuse promoted the recovery of muscle mass and power. However, they were not sufficient to restore muscle power to pre-disuse values in older individuals, suggesting that further countermeasures are required to counteract the disuse-induced loss of muscle power in older adults.

Abstract: Disuse-induced loss of muscle power can be detrimental in older individuals, seriously impairing functional capacity. In this study, we examined the changes in maximal explosive power (MEP) of lower limbs induced by a 14-day disuse (bed-rest, BR) and a subsequent 14-day retraining, to assess whether the impact of disuse was greater in older than in young men, and to analyse the causes of such adaptations. Sixteen older adults (Old: 55-65 years) and seven Young (18-30 years) individuals participated in this study. In a subgroup of eight Old subjects, countermeasures based on cognitive training and protein supplementation were applied. MEP was measured with an explosive ergometer, muscle mass was determined by magnetic resonance, motor control was studied by EMG, and single muscle fibres were analysed in vastus lateralis biopsy samples. MEP was ∼33% lower in Old than in Young individuals, and remained significantly lower (-19%) when normalized by muscle volume. BR significantly affected MEP in Old (-15%) but not in Young. Retraining tended to increase MEP; however, this intervention was not sufficient to restore pre-BR values in Old. Ankle co-contraction increased after BR in Old only, and remained elevated after retraining (+30%). Significant atrophy occurred in slow fibres in Old, and in fast fibres in Young. After retraining, the recovery of muscle fibre thickness was partial. The proposed countermeasures were not sufficient to affect muscle mass and power. The greater impact of disuse and smaller retraining-induced recovery observed in Old highlight the importance of designing suitable rehabilitation protocols for older individuals.
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http://dx.doi.org/10.1113/JP274772DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5813607PMC
February 2018

Identification and characterization of three novel mutations in the CASQ1 gene in four patients with tubular aggregate myopathy.

Hum Mutat 2017 12 26;38(12):1761-1773. Epub 2017 Sep 26.

Department of Molecular and Developmental Medicine, Molecular Medicine Section, University of Siena, Siena, Italy.

Here, we report the identification of three novel missense mutations in the calsequestrin-1 (CASQ1) gene in four patients with tubular aggregate myopathy. These CASQ1 mutations affect conserved amino acids in position 44 (p.(Asp44Asn)), 103 (p.(Gly103Asp)), and 385 (p.(Ile385Thr)). Functional studies, based on turbidity and dynamic light scattering measurements at increasing Ca concentrations, showed a reduced Ca -dependent aggregation for the CASQ1 protein containing p.Asp44Asn and p.Gly103Asp mutations and a slight increase in Ca -dependent aggregation for the p.Ile385Thr. Accordingly, limited trypsin proteolysis assay showed that p.Asp44Asn and p.Gly103Asp were more susceptible to trypsin cleavage in the presence of Ca in comparison with WT and p.Ile385Thr. Analysis of single muscle fibers of a patient carrying the p.Gly103Asp mutation showed a significant reduction in response to caffeine stimulation, compared with normal control fibers. Expression of CASQ1 mutations in eukaryotic cells revealed a reduced ability of all these CASQ1 mutants to store Ca and a reduced inhibitory effect of p.Ile385Thr and p.Asp44Asn on store operated Ca entry. These results widen the spectrum of skeletal muscle diseases associated with CASQ1 and indicate that these mutations affect properties critical for correct Ca handling in skeletal muscle fibers.
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http://dx.doi.org/10.1002/humu.23338DOI Listing
December 2017

Role of p66shc in skeletal muscle function.

Sci Rep 2017 07 24;7(1):6283. Epub 2017 Jul 24.

Department of Biomedical Sciences, University of Padua, Padua, Italy.

p66shc is a growth factor adaptor protein that contributes to mitochondrial ROS production. p66shc is involved in insulin signaling and its deletion exerts a protective effect against diet-induced obesity. In light of the role of skeletal muscle activity in the control of systemic metabolism and obesity, we investigated which is the contribution of p66shc in regulating muscle structure and function. Here, we show that p66shc muscles are undistinguishable from controls in terms of size, resistance to denervation-induced atrophy, and force. However, p66shc mice perform slightly better than wild type animals during repetitive downhill running. Analysis of the effects after placing mice on a high fat diet (HFD) regimen demonstrated that running distance is greatly reduced in obese wild type animals, but not in overweight-resistant p66shc mice. In addition, muscle force measured after exercise decreases upon HFD in wild type mice while p66shc animals are protected. Our data indicate that p66shc affect the response to damage of adult muscle in chow diet, and it determines the maintenance of muscle force and exercise performance upon a HFD regimen.
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http://dx.doi.org/10.1038/s41598-017-06363-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5524746PMC
July 2017

Single Muscle Fiber Proteomics Reveals Fiber-Type-Specific Features of Human Muscle Aging.

Cell Rep 2017 06;19(11):2396-2409

Max-Planck-Institute of Biochemistry, Martinsried 82152, Germany. Electronic address:

Skeletal muscle is a key tissue in human aging, which affects different muscle fiber types unequally. We developed a highly sensitive single muscle fiber proteomics workflow to study human aging and show that the senescence of slow and fast muscle fibers is characterized by diverging metabolic and protein quality control adaptations. Whereas mitochondrial content declines with aging in both fiber types, glycolysis and glycogen metabolism are upregulated in slow but downregulated in fast muscle fibers. Aging mitochondria decrease expression of the redox enzyme monoamine oxidase A. Slow fibers upregulate a subset of actin and myosin chaperones, whereas an opposite change happens in fast fibers. These changes in metabolism and sarcomere quality control may be related to the ability of slow, but not fast, muscle fibers to maintain their mass during aging. We conclude that single muscle fiber analysis by proteomics can elucidate pathophysiology in a sub-type-specific manner.
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http://dx.doi.org/10.1016/j.celrep.2017.05.054DOI Listing
June 2017

Neuromuscular electrical stimulation improves skeletal muscle regeneration through satellite cell fusion with myofibers in healthy elderly subjects.

J Appl Physiol (1985) 2017 Sep 1;123(3):501-512. Epub 2017 Jun 1.

Department of Neuroscience Imaging and Clinical Sciences, G. d'Annunzio University of Chieti-Pescara, Chieti, Italy.

The aim of this study was to determine whether neuromuscular electrical stimulation (NMES) affects skeletal muscle regeneration through a reduction of oxidative status in satellite cells of healthy elderly subjects. Satellite cells from the vastus lateralis skeletal muscle of 12 healthy elderly subjects before and after 8 wk of NMES were allowed to proliferate to provide myogenic populations of adult stem cells [myogenic precursor cells (MPCs)]. These MPCs were then investigated in terms of their proliferation, their basal cytoplasmic free Ca concentrations, and their expression of myogenic regulatory factors (, and ) and micro-RNAs (miR-1, miR-133a/b, and miR-206). The oxidative status of these MPCs was evaluated through superoxide anion production and superoxide dismutase and glutathione peroxidase activities. On dissected single skeletal myofibers, the nuclei were counted to determine the myonuclear density, the fiber phenotype, cross-sectional area, and tension developed. The MPCs obtained after NMES showed increased proliferation rates along with increased cytoplasmic free Ca concentrations and gene expression of and on MPCs. Muscle-specific miR-1, miR-133a/b, and miR-206 were upregulated. This NMES significantly reduced superoxide anion production, along with a trend to reduction of superoxide dismutase activity. The NMES-dependent stimulation of muscle regeneration enhanced satellite cell fusion with mature skeletal fibers. NMES improved the regenerative capacity of skeletal muscle in elderly subjects. Accordingly, the skeletal muscle strength and mobility of NMES-stimulated elderly subjects significantly improved. NMES may thus be further considered for clinical or ageing populations. The neuromuscular electrical stimulation (NMES) effect on skeletal muscle regeneration was assessed in healthy elderly subjects for the first time. NMES improved the regenerative capacity of skeletal muscle through increased myogenic precursor cell proliferation and fusion with mature myofibers. The increased cytoplasmic free Ca concentration along with , , and micro-RNA upregulation could be related to reduced O production, which, in turn, favors myogenic regeneration. Accordingly, the skeletal muscle strength of NMES-stimulated lower limbs of healthy elderly subjects improved along with their mobility.
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http://dx.doi.org/10.1152/japplphysiol.00855.2016DOI Listing
September 2017

FoxO-dependent atrogenes vary among catabolic conditions and play a key role in muscle atrophy induced by hindlimb suspension.

J Physiol 2017 02 12;595(4):1143-1158. Epub 2016 Dec 12.

Department of Molecular Medicine, University of Pavia, Pavia, Italy.

Key Points: Muscle atrophy is a debilitating condition that affects a high percentage of the population with a negative impact on quality of life. Dissecting the molecular level of the atrophy process, and the similarities/dissimilarities among different catabolic conditions, is a necessary step for designing specific countermeasures to attenuate/prevent muscle loss. The FoxO family transcription factors represent one of the most important regulators of atrophy programme stimulating the expression of many atrophy-related genes. The findings of the present study clearly indicate that the signalling network controlling the atrophy programme is specific for each catabolic condition.

Abstract: Muscle atrophy is a complex process that is in common with many different catabolic diseases including disuse/inactivity and ageing. The signalling pathways that control the atrophy programme in the different disuse/inactivity conditions have not yet been completely dissected. The inhibition of FoxO is considered to only partially spare muscle mass after denervation. The present study aimed: (i) to determine the involvement of FoxOs in hindlimb suspension disuse model; (ii) to define whether the molecular events of protein breakdown are shared among different unloaded muscles; and finally (iii) to compare the data obtained in this model with another model of inactivity such as denervation. Both wild-type and muscle-specific FoxO1,3,4 knockout (FoxO1,3,4 ) mice were unloaded for 3 and 14 days and muscles were characterized by functional, morphological, biochemical and molecular assays. The data obtained show that FoxOs are required for muscle loss and force drop during unloading. Moreover, we found that FoxO-dependent atrogenes vary in different unloaded muscles and that they diverge from denervation. The findings of the present study clearly indicate that the signalling network that controls the atrophy programme is specific for each catabolic condition.
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http://dx.doi.org/10.1113/JP273097DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5309360PMC
February 2017

The Regenerative Potential of Female Skeletal Muscle upon Hypobaric Hypoxic Exposure.

Front Physiol 2016 14;7:303. Epub 2016 Jul 14.

Department of Neuroscience, Imaging and Clinical Sciences, G. d'Annunzio University of Chieti-PescaraChieti, Italy; Laboratory of Functional Evaluation, University 'G. d'Annunzio', Chieti-PescaraChieti, Italy; Interuniversity Institute of MyologyChieti, Italy.

Aim: The aim of this study was to determine whether a 14-day trekking expeditions, in high altitude hypoxic environment, triggers redox disturbance at the level of satellite cells (adult stem cells) in young women.

Methods: We collected muscle biopsies from Vastus Lateralis muscle for both single fiber analysis and satellite cells isolation. The samples collected before (PRE-Hypoxia) and after (POST-Hypoxia) the trekking in the Himalayas were compared. Satellite cells were investigated for oxidative stress (oxidant production, antioxidant enzyme activity, and lipid damage), mitochondrial potential variation, gene profile of HIF, and myogenic transcription factors (Pax7, MyoD, myogenin), and miRNA expression (miR-1, miR-133, miR-206).

Results: The nuclear domain analysis showed a significant fusion and consequent reduction of the Pax7(+) satellite cells in the single mature fibers. The POST-Hypoxia myoblasts obtained by two out of six volunteers showed high superoxide anion production and lipid peroxidation along with impaired dismutase and catalase and mitochondrial potential. The transcription profile and miRNA expression were different for oxidized and non-oxidized cells.

Conclusions: The present study supports the phenomenon of hypobaric-hypoxia-induced oxidative stress and its role in the impairment of the regenerative capacity of satellite cells derived from the V. Lateralis muscle of young adult female subjects.
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http://dx.doi.org/10.3389/fphys.2016.00303DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4943944PMC
July 2016

Protein Supplementation Does Not Further Increase Latissimus Dorsi Muscle Fiber Hypertrophy after Eight Weeks of Resistance Training in Novice Subjects, but Partially Counteracts the Fast-to-Slow Muscle Fiber Transition.

Nutrients 2016 Jun 1;8(6). Epub 2016 Jun 1.

Department of Biomedical Sciences, University of Padova, Padova 35131, Italy.

The response to resistance training and protein supplementation in the latissimus dorsi muscle (LDM) has never been investigated. We investigated the effects of resistance training (RT) and protein supplementation on muscle mass, strength, and fiber characteristics of the LDM. Eighteen healthy young subjects were randomly assigned to a progressive eight-week RT program with a normal protein diet (NP) or high protein diet (HP) (NP 0.85 vs. HP 1.8 g of protein·kg(-1)·day(-1)). One repetition maximum tests, magnetic resonance imaging for cross-sectional muscle area (CSA), body composition, and single muscle fibers mechanical and phenotype characteristics were measured. RT induced a significant gain in strength (+17%, p < 0.0001), whole muscle CSA (p = 0.024), and single muscle fibers CSA (p < 0.05) of LDM in all subjects. Fiber isometric force increased in proportion to CSA (+22%, p < 0.005) and thus no change in specific tension occurred. A significant transition from 2X to 2A myosin expression was induced by training. The protein supplementation showed no significant effects on all measured outcomes except for a smaller reduction of 2X myosin expression. Our results suggest that in LDM protein supplementation does not further enhance RT-induced muscle fiber hypertrophy nor influence mechanic muscle fiber characteristics but partially counteracts the fast-to-slow fiber shift.
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http://dx.doi.org/10.3390/nu8060331DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4924172PMC
June 2016

Expression and identification of 10 sarcomeric MyHC isoforms in human skeletal muscles of different embryological origin. Diversity and similarity in mammalian species.

Ann Anat 2016 Sep 9;207:9-20. Epub 2016 Mar 9.

Department of Comparative Biomedicine and Food Science, University of Padova, viale dell'Università 16, Legnaro, 35020 Padova, Italy.

In the mammalian genome, among myosin heavy chain (MyHC) isoforms a family can be identified as sarcomeric based on their molecular structure which allows thick filament formation. In this study we aimed to assess the expression of the 10 sarcomeric isoforms in human skeletal muscles, adopting this species as a reference for comparison with all other mammalian species. To this aim, we set up the condition for quantitative Real Time PCR assay to detect and quantify MyHC mRNA expression in a wide variety of human muscles from somitic, presomitic and preotic origin. Specific patterns of expression of the following genes MYH1, MYH2, MYH3, MYH4, MYH6, MYH7, MYH8, MYH13, MYH14/7b and MYH15 were demonstrated in various muscle samples. On the same muscle samples which were analysed for mRNA expression, the corresponding MyHC proteins were studied with SDS PAGE and Western blot. The mRNA-protein comparison allowed the identification of 10 distinct proteins based on the electrophoretic migration rate. Three groups were formed based on the migration rate: fast migrating comprising beta/slow/1, alpha cardiac and fast 2B, slow migrating comprising fast 2X, fast 2A and two developmental isoforms (NEO and EMB), intermediate migrating comprising EO MyHC, slow B (product of MYH15), slow tonic (product of MYH14/7b). Of special interest was the demonstration of a protein band corresponding to 2B-MyHC in laryngeal muscles and the finding that all 10 isoforms are expressed in extraocular muscles. These latter muscles are the unique localization for extraocular, slow B (product of MYH15) and slow tonic (product of MYH14/7b).
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http://dx.doi.org/10.1016/j.aanat.2016.02.007DOI Listing
September 2016

Greater loss in muscle mass and function but smaller metabolic alterations in older compared with younger men following 2 wk of bed rest and recovery.

J Appl Physiol (1985) 2016 Apr 28;120(8):922-9. Epub 2016 Jan 28.

Institute for Kinesiology Research, Science and Research Centre, University of Primorska, Koper, Slovenia;

This investigation aimed to compare the response of young and older adult men to bed rest (BR) and subsequent rehabilitation (R). Sixteen older (OM, age 55-65 yr) and seven young (YM, age 18-30 yr) men were exposed to a 14-day period of BR followed by 14 days of R. Quadriceps muscle volume (QVOL), force (QF), and explosive power (QP) of leg extensors; single-fiber isometric force (Fo); peak aerobic power (V̇o2peak); gait stride length; and three metabolic parameters, Matsuda index of insulin sensitivity, postprandial lipid curve, and homocysteine plasma level, were measured before and after BR and after R. Following BR, QVOL was smaller in OM (-8.3%) than in YM (-5.7%,P= 0.031); QF (-13.2%,P= 0.001), QP (-12.3%,P= 0.001), and gait stride length (-9.9%,P= 0.002) were smaller only in OM. Fo was significantly smaller in both YM (-32.0%) and OM (-16.4%) without significant differences between groups. V̇o2peakdecreased more in OM (-15.3%) than in YM (-7.6%,P< 0.001). Instead, the Matsuda index fell to a greater extent in YM than in OM (-46.0% vs. -19.8%, respectively,P= 0.003), whereas increases in postprandial lipid curve (+47.2%,P= 0.013) and homocysteine concentration (+26.3%,P= 0.027) were observed only in YM. Importantly, after R, the recovery of several parameters, among them QVOL, QP, and V̇o2peak, was not complete in OM, whereas Fo did not recover in either age group. The results show that the effect of inactivity on muscle mass and function is greater in OM, whereas metabolic alterations are greater in YM. Furthermore, these findings show that the recovery of preinactivity conditions is slower in OM.
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http://dx.doi.org/10.1152/japplphysiol.00858.2015DOI Listing
April 2016

Age-dependent neuromuscular impairment in prion protein knockout mice.

Muscle Nerve 2016 Feb 26;53(2):269-79. Epub 2015 Nov 26.

Department of Biomedical Sciences, University of Padova, Via U. Bassi 58/B, 35131, Padova, Italy.

Introduction: The cellular prion protein (PrP(C) ) is commonly recognized as the precursor of prions, the infectious agents of the fatal transmissible spongiform encephalopathies, or prion diseases. Despite extensive effort, the physiological role of PrP(C) is still ambiguous. Evidence has suggested that PrP(C) is involved in different cellular functions, including peripheral nerve integrity and skeletal muscle physiology.

Methods: We analyzed the age-dependent influence of PrP(C) on treadmill test-based aerobic exercise capacity and on a series of morphological and metabolic parameters using wild-type and genetically modified mice of different ages expressing, or knockout (KO) for, PrP(C) .

Results: We found that aged PrP-KO mice displayed a reduction in treadmill performance compared with PrP-expressing animals, which was associated with peripheral nerve demyelination and alterations of skeletal muscle fiber type.

Conclusion: PrP-KO mice have an age-dependent impairment of aerobic performance as a consequence of specific peripheral nerve and muscle alterations.
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http://dx.doi.org/10.1002/mus.24708DOI Listing
February 2016

Protein supplementation increases postexercise plasma myostatin concentration after 8 weeks of resistance training in young physically active subjects.

J Med Food 2015 Jan;18(1):137-43

1 Department of Biomedical Sciences (DBS), University of Padova , Padova, Italy .

Myostatin (MSTN) is a negative regulator of muscle growth even if some studies have shown a counterintuitive positive correlation between MSTN and muscle mass (MM). Our aim was to investigate the influence of 2 months of resistance training (RT) and diets with different protein contents on plasma MSTN, interleukin 1 beta (IL-1β), interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), and insulin-like growth factor 1 (IGF-1). Eighteen healthy volunteers were randomly divided in two groups: high protein (HP) and normal protein (NP) groups. Different protein diet contents were 1.8 and 0.85 g of protein·kg bw(-1)·day(-1) for HP and NP, respectively. Subjects underwent 8 weeks of standardized progressive RT. MSTN, IGF-1, IL-1β, IL-6, and TNF-α were analyzed before and after the first and the last training sessions. Lean body mass, MM, upper-limb muscle area, and strength were measured. Plasma MSTN showed a significant increase (P<.001) after the last training in the HP group compared with NP group and with starting value. IGF-1 plasma concentration showed a positive correlation with MSTN in HP after the last training (r(2)=0.6456; P=.0295). No significant differences were found between NP and HP for IL-1β, IL-6, TNF-α, and strength and MM or area. These findings suggest a "paradoxical" postexercise increase of plasma MSTN after 8 weeks of RT and HP diets. This MSTN elevation correlates positively with IGF-1 plasma level. This double increase of opposite (catabolic/anabolic) mediators could explain the substantial overlapping of MM increases in the two groups.
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http://dx.doi.org/10.1089/jmf.2014.0004DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4281872PMC
January 2015

A mutation in the CASQ1 gene causes a vacuolar myopathy with accumulation of sarcoplasmic reticulum protein aggregates.

Hum Mutat 2014 Oct 10;35(10):1163-70. Epub 2014 Sep 10.

Molecular Medicine Section, Department of Molecular and Developmental Medicine, University of Siena and Azienda Ospedaliera Universitaria Senese, Siena, 53100, Italy; IIM, Interuniversity Institute of Myology.

A missense mutation in the calsequestrin-1 gene (CASQ1) was found in a group of patients with a myopathy characterized by weakness, fatigue, and the presence of large vacuoles containing characteristic inclusions resulting from the aggregation of sarcoplasmic reticulum (SR) proteins. The mutation affects a conserved aspartic acid in position 244 (p.Asp244Gly) located in one of the high-affinity Ca(2+) -binding sites of CASQ1 and alters the kinetics of Ca(2+) release in muscle fibers. Expression of the mutated CASQ1 protein in COS-7 cells showed a markedly reduced ability in forming elongated polymers, whereas both in cultured myotubes and in in vivo mouse fibers induced the formation of electron-dense SR vacuoles containing aggregates of the mutant CASQ1 protein that resemble those observed in muscle biopsies of patients. Altogether, these results support the view that a single missense mutation in the CASQ1 gene causes the formation of abnormal SR vacuoles containing aggregates of CASQ1, and other SR proteins, results in altered Ca(2+) release in skeletal muscle fibers, and, hence, is responsible for the clinical phenotype observed in these patients.
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http://dx.doi.org/10.1002/humu.22631DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4177304PMC
October 2014

Effect of hyperbaric oxygenation and gemcitabine on apoptosis of pancreatic ductal tumor cells in vitro.

Anticancer Res 2013 Nov;33(11):4827-32

Department of Anesthesiology, SUNY Upstate Medical University, Syracuse, NY, 13210, U.S.A.

Background: Gemcitabine is first-line therapy for advanced pancreatic ductal adenocarcinoma (PDAC) with a poor survival and response rate. Hyperbaric oxygenation (HBO) enhances delivery of oxygen to hypoxic tumor cells and increases their susceptibility to cytotoxic effects of chemotherapy. We hypothesized that the anticancer activity of gemcitabine (GEM) may be enhanced if tumor cells are placed in an oxygen-rich environment. The present study evaluated the effects of gemcitabine, HBO and their combination on apoptosis of tumor cells.

Materials And Methods: PANC-1 and AsPc-1 PDAC tumor cell lines were used. Cultured tumor cells were treated with GEM at its growth-inhibitory concentration (IC50) and HBO at 2.5 ATA for 90 min or a combination of both (HBO then GEM and GEM then HBO). Twenty-four hours later, apoptotic cells in each group were analyzed and the apoptotic index (AI) was calculated.

Results: PANC-1 cell line: HBO alone had no effect on AI: 6.5 ± 0.1 vs. 5.9 ± 0.1. HBO before and after gemcitabine did not further increase AI: 8.2 ± 0.1 (HBO-GEM), 8.5 ± 0.1 (GEM-HBO) vs. 8.1 ± 0.1 (GEM). The combination of HBO and gemcitabine significantly increased AI: 10.7 ± 0.02 (p<0.001 vs. all groups). AsPc-1 cell line: HBO-alone had no effect on AI: 5.9 ± 0.1 vs. 5.9 ± 0.1. HBO before and after gemcitabine did not further increase AI: 8.2 ± 0.1 (HBO-GEM), 8.4 ± 0.1 (GEM-HBO) vs. 8.0 ± 0.1 (GEM). The combination of HBO and gemcitabine significantly increased AI: 9.7 ± 0.1 (p<0.001 vs. all groups).

Conclusion: HBO-alone, whether administered before and after gemcitabine has no effect on apoptosis of PDAC cells in vitro. HBO significantly enhanced gemcitabine-induced apoptosis when administered during gemcitabine. Our findings suggest that the time window would be critical for using HBO as adjuvant to chemotherapy.
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November 2013

Mitochondrial Ca2+-handling in fast skeletal muscle fibers from wild type and calsequestrin-null mice.

PLoS One 2013 3;8(10):e74919. Epub 2013 Oct 3.

Department of Biomedical Sciences and Interuniversity Institute of Myology (IIM), University of Padova, Padua, Italy.

Mitochondrial calcium handling and its relation with calcium released from sarcoplasmic reticulum (SR) in muscle tissue are subject of lively debate. In this study we aimed to clarify how the SR determines mitochondrial calcium handling using dCASQ-null mice which lack both isoforms of the major Ca(2+)-binding protein inside SR, calsequestrin. Mitochondrial free Ca(2+)-concentration ([Ca(2+)]mito) was determined by means of a genetically targeted ratiometric FRET-based probe. Electron microscopy revealed a highly significant increase in intermyofibrillar mitochondria (+55%) and augmented coupling (+12%) between Ca(2+) release units of the SR and mitochondria in dCASQ-null vs. WT fibers. Significant differences in the baseline [Ca(2+)]mito were observed between quiescent WT and dCASQ-null fibers, but not in the resting cytosolic Ca(2+) concentration. The rise in [Ca(2+)]mito during electrical stimulation occurred in 20-30 ms, while the decline during and after stimulation was governed by 4 rate constants of approximately 40, 1.6, 0.2 and 0.03 s(-1). Accordingly, frequency-dependent increase in [Ca(2+)]mito occurred during sustained contractions. In dCASQ-null fibers the increases in [Ca(2+)]mito were less pronounced than in WT fibers and even lower when extracellular calcium was removed. The amplitude and duration of [Ca(2+)]mito transients were increased by inhibition of mitochondrial Na(+)/Ca(2+) exchanger (mNCX). These results provide direct evidence for fast Ca(2+) accumulation inside the mitochondria, involvement of the mNCX in mitochondrial Ca(2+)-handling and a dependence of mitochondrial Ca(2+)-handling on intracellular (SR) and external Ca(2+) stores in fast skeletal muscle fibers. dCASQ-null mice represent a model for malignant hyperthermia. The differences in structure and in mitochondrial function observed relative to WT may represent compensatory mechanisms for the disease-related reduction of calcium storage capacity of the SR and/or SR Ca(2+)-leakage.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0074919PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3789688PMC
June 2014

BMP signaling controls muscle mass.

Nat Genet 2013 Nov 29;45(11):1309-18. Epub 2013 Sep 29.

1] Dulbecco Telethon Institute at the Venetian Institute of Molecular Medicine, Padova, Italy. [2] Department of Biomedical Sciences, University of Padova, Padova, Italy. [3].

Cell size is determined by the balance between protein synthesis and degradation. This equilibrium is affected by hormones, nutrients, energy levels, mechanical stress and cytokines. Mutations that inactivate myostatin lead to excessive muscle growth in animals and humans, but the signals and pathways responsible for this hypertrophy remain largely unknown. Here we show that bone morphogenetic protein (BMP) signaling, acting through Smad1, Smad5 and Smad8 (Smad1/5/8), is the fundamental hypertrophic signal in mice. Inhibition of BMP signaling causes muscle atrophy, abolishes the hypertrophic phenotype of myostatin-deficient mice and strongly exacerbates the effects of denervation and fasting. BMP-Smad1/5/8 signaling negatively regulates a gene (Fbxo30) that encodes a ubiquitin ligase required for muscle loss, which we named muscle ubiquitin ligase of the SCF complex in atrophy-1 (MUSA1). Collectively, these data identify a critical role for the BMP pathway in adult muscle maintenance, growth and atrophy.
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http://dx.doi.org/10.1038/ng.2772DOI Listing
November 2013

Myosin isoforms and contractile properties of single fibers of human Latissimus Dorsi muscle.

Biomed Res Int 2013 22;2013:249398. Epub 2013 Jul 22.

Department of Biomedical Sciences, University of Padova, Padova, Italy.

The aim of our study was to investigate fiber type distribution and contractile characteristics of Latissimus Dorsi muscle (LDM). Samples were collected from 18 young healthy subjects (9 males and 9 females) through percutaneous fine needle muscle biopsy. The results showed a predominance of fast myosin heavy chain isoforms (MyHC) with 42% of MyHC 2A and 25% of MyHC 2X, while MyHC 1 represented only 33%. The unbalance toward fast isoforms was even greater in males (71%) than in females (64%). Fiber type distribution partially reflected MyHC isoform distribution with 28% type 1/slow fibers and 5% hybrid 1/2A fibers, while fast fibers were divided into 30% type 2A, 31% type A/X, 4% type X, and 2% type 1/2X. Type 1/slow fibers were not only less abundant but also smaller in cross-sectional area than fast fibers. During maximal isometric contraction, type 1/slow fibers developed force and tension significantly lower than the two major groups of fast fibers. In conclusion, the predominance of fast fibers and their greater size and strength compared to slow fibers reveal that LDM is a muscle specialized mainly in phasic and powerful activity. Importantly, such specialization is more pronounced in males than in females.
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http://dx.doi.org/10.1155/2013/249398DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3736486PMC
February 2014

Inflammation in muscular dystrophy and the beneficial effects of non-steroidal anti-inflammatory drugs.

Muscle Nerve 2012 Nov 27;46(5):773-84. Epub 2012 Jul 27.

DAHFMO Unit of Histology and Medical Embryology, Sapienza University, Via A. Scarpa 14-00161 Rome, Italy.

Introduction: Glucocorticoids are the only drugs available for the treatment of Duchenne muscular dystrophy (DMD), but it is unclear whether their efficacy is dependent on their anti-inflammatory activity.

Methods: To address this issue, mdx mice were treated daily with methylprednisolone and non-steroidal anti-inflammatory drugs (NSAIDs: aspirin, ibuprofen, parecoxib).

Results: NSAID treatment was effective in ameliorating muscle morphology and reducing macrophage infiltration and necrosis. The percentage of regenerating myofibers was not modified by the treatments. The drugs were effective in reducing COX-2 expression and inflammatory cytokines, but they did not affect utrophin levels. The effects of the treatments on contractile performance were analyzed. Isometric tension did not differ in treated and untreated muscle, but the resistance to fatigue was decreased by treatment with methylprednisolone and aspirin.

Conclusions: NSAIDs have a beneficial effect on mdx muscle morphology, pointing to a crucial role of inflammation in the progression of DMD.
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http://dx.doi.org/10.1002/mus.23432DOI Listing
November 2012

S1P2 receptor promotes mouse skeletal muscle regeneration.

J Appl Physiol (1985) 2012 Sep 28;113(5):707-13. Epub 2012 Jun 28.

Department of Biomedical Sciences, University of Padova, Padova, Italy.

Sphingosine 1-phosphate is a bioactive lipid that modulates skeletal muscle growth through its interaction with specific receptors localized in the cell membrane of muscle fibers and satellite cells. This study analyzes the role of S1P(2) receptor during in vivo regeneration of soleus muscle in two models of S1P(2) deficiency: the S1P(2)-null mouse and wild-type mice systemically treated with the S1P(2) receptor antagonist JTE-013. To stimulate regeneration, muscle degeneration was induced by injecting into soleus muscle the myotoxic drug notexin. Both ablation of S1P(2) receptor and its functional inactivation delayed regeneration of soleus muscle. The exogenous supplementation of S1P or its removal, by a specific antibody, two conditions known to stimulate or inhibit, respectively, soleus muscle regeneration, were without effects when the S1P(2) receptor was absent or inactive. The delayed regeneration was associated with a lower level of myogenin, a muscle differentiation marker, and reduced phosphorylation of Akt, a key marker of muscle growth. Consistently, silencing of S1P(2) receptor abrogated the pro-myogenic action of S1P in satellite cells, paralleled by low levels of the myogenic transcription factor myogenin. The study indicates that S1P(2) receptor plays a key role in the early phases of muscle regeneration by sustaining differentiation and growth of new-forming myofibers.
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http://dx.doi.org/10.1152/japplphysiol.00300.2012DOI Listing
September 2012

Latissimus dorsi fine needle muscle biopsy: a novel and efficient approach to study proximal muscles of upper limbs.

J Surg Res 2010 Dec 12;164(2):e257-63. Epub 2010 Jun 12.

Department of Anatomy and Physiology, University of Padova, Padova, Italy.

Background: The muscle biopsy based on the Bergström needle has been widely used for more than 40 y for diagnosis and experimental studies on muscle. More recently, thinner needles and tru-cut needles have also been introduced. Such techniques have been largely tested on various muscles, including the quadriceps, with few studies on upper limb muscles like deltoid, and no studies on latissimus dorsi muscle (LDM). In this study, we implemented and validated a protocol to collect samples of LDM for experimental purposes, causing minimal discomfort to volunteers. Two main problems were considered: the anatomical localization of the biopsy site and the selection of an appropriate needle.

Material And Methods: A strict protocol of palpatory anatomy was adopted and validated with ultrasonography to localize the biopsy site in LDM in subjects with various degrees of muscle development. A 14 gauge tru-cut needle was selected as the smallest and still effective device for sampling. Biopsy sampling was performed in 18 subjects without any complications, or complains of pain or functional limitations.

Results: Approximately 4 mg of tissue were recovered from each introduction of the inner notched cannula of the needle. With three consecutive samplings, an amount of tissue sufficient to prepare proteins for gel electrophoresis and Western blot and to dissect single fiber segment for functional experiments, was obtained.

Conclusions: Taken together, the results suggest that this biopsy technique opens to experimental studies muscles until now never considered accessible.
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http://dx.doi.org/10.1016/j.jss.2010.05.043DOI Listing
December 2010