Myostatin and plasticity of skeletal muscle tissue

Skeletal muscle is an extremely plastic tissue for its ability to respond to different stimuli such as physiological variation and external stress. Muscle hypertrophy involves an increase in muscle mass, changes in myofibril composition and adaptation of metabolic pathways. Plasticity of skeletal muscle in response to exercise training is also caused by proliferation and differentiation of the satellite muscle stem cells in response to various growth and differentiation factors. This process is mainly mediated by myokines secreted during skeletal muscle contraction. Myokines are proteins that act as hormones both locally in the muscle and/or in an endocrine manner in other organs, mainly liver, brain and adipose tissue. Myostatin, known as growth differentiation factor-8, a myokine member of transforming growth factor-b (TGF-b) superfamily, can act on muscle cells in an autocrine manner leading to inhibition of muscle myogenesis. Muscle myostatin expression and its plasma concentration are downregulated after acute and long-term physical exercise thus allowing muscle hypertrophy. In addition, myostatin is correlated to obesity and insulin resistance for its ability to affect energy metabolism and insulin-sensitivity in muscle cells, respectively. These findings reveal that myostatin may have potential therapeutic applications to treat muscle atrophy diseases in humans. Even in sports, drugs able to inhibit myostatin expression can lead athletes to increase their sport performance. Here, we present a brief overview of myostatin and its role in biological mechanisms involved in exercise-induced plasticity of skeletal muscle

Thrombin mutants with altered enzymatic activity have an impaired mitogenic effect on mouse fibroblasts and are inefficient modulators of stellation of rat cortical astrocytes

AbstractWe produced recombinant human thrombin mutants to investigate the correlation between the thrombin enzyme and mitogenic activity. Single amino acid substitutions were introduced in the catalytic triad (H43N, D99N, S205A, S205T), in the oxy-anion binding site (G203A) and in the anion binding exosite-1 region (R73E). Proteins were produced as prethrombin-2 mutants secreted in the culture medium of DXB11-derived cell lines. All mutants were activated by ecarin to the corresponding thrombin mutants; the enzymatic activity was assayed on a chromogenic substrate and on the procoagulant substrate fibrinogen. Mutations S205A and G203A completely abolished the enzyme activity. Mutations H43N, D99N and S205T dramatically impaired the enzyme activity toward both substrates. The R73E mutation dissociated the amidolytic activity and the clotting activity of the protein. The ability of thrombin mutants to induce proliferation was investigated in NIH3T3 mouse fibroblasts and rat cortical astrocytes. The ability of the thrombin mutants to revert astrocyte stellation was also studied. The mitogenic activity and the effect on the astrocyte stellation of the thrombin mutants correlated with their enzymatic activity. Furthermore the receptor occupancy by the inactive S205A mutant prevented the thrombin effects providing strong evidence that a proteolytically activated receptor is involved in cellular responses to thrombin

Circadian rhythms, physical activity and longevity

Human health implies complex mechanisms and involves diseases prevention aimed at ensuring a psycho-physical wellbeing homoeostasis. The search for longevity can be related to the slowdown in aging, and psycho-physical wellbeing is often related to the lifestyle, mainly to the human physical activity and nutrition. Circadian rhythms are processes that affect the behaviour, physiology and metabolism of mammals across cyclic periods of 24 hours. These rhythms are regulated by multiple physiological systems, whose key elements are the alternation between light and dark and between food consumption and periods of fasting. Therefore, during evolution, a constant adaptation to natural rhythms by humans has been established towards the surrounding environment determining periods of food consumption and periods of fasting coinciding with rest. Recent sociological surveys have shown that there is a slight increase in the number of people who devote themselves to a constant physical/sport activity, but this is an ephemeral percentage compared to the dramatic increase in the incidence of diseases related to aging such as obesity and diabetes, easily preventable with healthy lifestyles. Therefore, the connection between circadian rhythms, physical activity and lifestyles represents an important feature involved in human longevity. Here, a survive of the biological mechanisms, implied in this behaviour, is presented

METODO PER LA PREPARAZIONE DI LIPOCORTINA 1 UMANA

Si descrive un processo per la preparazione di Lipocortina 1 ricombinante umana, che comprende: a) la coltura di un ceppo di E. coli recante un gene codificante RNA polimerasi di T7 sotto controllo di un promotore inducibile, detto ceppo essendo stato trasformato da un vettore plasmidico in cui il gene codificante la Lipocortina 1 è sotto controllo di un promotore di T7; b) l'isolamento e la purificazione della Lipocortina 1 ricombinante dalla coltura del ceppo trasformato

PHYSICAL ACTIVITY AND COGNITIVE FUNCTIONS: ROLE OF THE BRAIN-DERIVED NEUROTROPHIC FACTOR (BDNF)

The skeletal muscle is considered an endocrine organ as it secretes various myokines. The myokines are produced during skeletal muscle contraction and exert autocrine, paracrine, and endocrine effects even on different organs and tissues. Up to now, many myokines have been described, including the brain-derived neurotrophic factor (BDNF), interleukin-6 (IL-6), irisin, leukemia inhibitory factor (LIF), and insulin-like growth factor1 (IGF-1) are the most relevant also for brain functions. In particular, it is well known that BDNF ameliorates cognitive functions via neuronal differentiation and plasticity in the hippocampal region. Therefore, myokines represent key molecules in the cross-talk between skeletal muscle and brain

The N-terminal domain of 2',3'-cyclic nucleotide 3'-phosphodiesterase harbors a GTP/ATP binding site

The interaction between 2',3'-cyclic nucleotide 3'-phosphodiesterase and guanine/adenine nucleotides was investigated. The binding of purine nucleotides to 2',3'-cyclic nucleotide 3'-phosphodiesterase was revealed by both direct and indirect methods. In fact, surface plasmon resonance experiments, triphosphatase activity measurements, and fluorescence experiments revealed that 2',3'-cyclic nucleotide 3'-phosphodiesterase binds purine nucleotide triphosphates with an affinity higher than that displayed for diphosphates; on the contrary, the affinity for both purine monophosphates and pyrimidine nucleotides was negligible. An interpretation of biological experimental data was achieved by a building of 2',3'-cyclic nucleotide 3'-phosphodiesterase N-terminal molecular model. The structural elements responsible for nucleotide binding were identified and potential complexes between the N-terminal domain of CNP-ase and nucleotide were analyzed by docking simulations. Therefore, our findings suggest new functional and structural property of the N-terminal domain of CNPase

Interleukin-6 induced astrocytic differentiation modulates Mannose Binding Lectin (MBL)-Associated Serine Protease (MASP)-1 and MASP-3 expression in C6 glioma cells

Among inflammatory cytokines, Interleukin-6 (IL-6) shows a pleiotropic nature acting as a mediator in differentiation, immune response and diseases within the Central Nervous System (CNS). Exposure to exogenous or autocrine IL-6, induced by cAMP, promotes astrocytic differentiation of glioma C6 cells which assume an astrocytic phenotype correlated to the expression of glial fibrillary acidic protein (GFAP). In addition, in several mouse models of brain injury, the up-regulation of IL-6 expression was correlated to the innate and acquired immunity. Glioma cells also express Mannose-Binding Lectin (MBL)-Associated Serine Proteases (MASP)-1 and 3, involved in the activation of the lectin complement pathway (LCP) in innate immunity. We investigated MASP-1 and MASP-3 expression during IL-6 and dibutyryl cAMP (dbcAMP) induced astrocytic differentiation in C6 cells. As previously reported, IL-6 or dbcAMP promoted a change in C6 cell morphology towards an astrocytic phenotype, as confirmed by the increase in GFAP expression levels. During this differentiation process, we observed a highly increase in MASP-1 and MASP-3 mRNA and protein expression levels compared to untreated cells. To investigate the involvement of protein kinase A (PKA) signalling pathway in IL-6 induced effects, C6 cells were pre-treated with the H89 (PKA) inhibitor. This exposure caused an inhibition in the astrocytic differentiation and a decrease both in STAT3 phosphorylation levels and MASP-1/MASP-3 expression levels. Taken together, these results strongly suggest that IL-6 might act as a regulatory cytokine in innate immunity enhancing MASP-1 and MASP-3 expression level through PKA signalling in C6 cells