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

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

Improving Protein Crystal Quality by the Without-Oil Microbatch Method: Crystallization and Preliminary X-ray Diffraction Analysis of Glutathione Synthetase from Pseudoalteromonas haloplanktis

Glutathione synthetases catalyze the ATP-dependent synthesis of glutathione from l-γ-glutamyl- l-cysteine and glycine. Although these enzymes have been sequenced and characterized from a variety of biological sources, their exact catalytic mechanism is not fully understood and nothing is known about their adaptation at extremophilic environments. Glutathione synthetase from the Antarctic eubacterium Pseudoalteromonas haloplanktis (PhGshB) has been expressed, purified and successfully crystallized. An overall improvement of the crystal quality has been obtained by adapting the crystal growth conditions found with vapor diffusion experiments to the without-oil microbatch method. The best crystals of PhGshB diffract to 2.34 Å resolution and belong to space group P212121, with unit-cell parameters a = 83.28 Å, b = 119.88 Å, c = 159.82 Å. Refinement of the model, obtained using phases derived from the structure of the same enzyme from Escherichia coli by molecular replacement, is in progress. The structural determination will provide the first structural characterization of a psychrophilic glutathione synthetase reported to date

Diclofenac-Induced Apoptosis in the Neuroblastoma Cell Line SH-SY5Y: Possible Involvement of the Mitochondrial Superoxide Dismutase

Diclofenac, a nonsteroidal anti-inflammatory drug, induces apoptosis on the neuroblastoma cell line SH-SY5Y through a mitochondrial dysfunction, affecting some antioxidant mechanisms. Indeed, the time- and dose-dependent increase of apoptosis is associated to an early enhancement of the reactive oxygen species (ROS). Mitochondrial superoxide dismutase (SOD2) plays a crucial role in the defence against ROS, thus protecting against several apoptotic stimuli. Diclofenac decreased the protein levels and the enzymatic activity of SOD2, without any significant impairment of the corresponding mRNA levels in the SH-SY5Y extracts. When cells were incubated with an archaeal exogenous thioredoxin, an attenuation of the diclofenac-induced apoptosis was observed, together with an increase of SOD2 protein levels. Furthermore, diclofenac impaired the mitochondrial membrane potential, leading to a release of cytochrome c. These data suggest that mitochondria are involved in the diclofenac-induced apoptosis of SH-SY5Y cells and point to a possible role of SOD2 in this process

Mitochondrial diabetes in children: seek and you will find it

Maternally Inherited Diabetes and Deafness (MIDD) is a rare form of diabetes due to defects in mitochondrial DNA (mtDNA). 3243 A.G is the mutation most frequently associated with this condition, but other mtDNA variants have been linked with a diabetic phenotype suggestive of MIDD. From 1989 to 2009, we clinically diagnosed mitochondrial diabetes in 11 diabetic children. Diagnosis was based on the presence of one or more of the following criteria: 1) maculopathy; 2) hearing impairment; 3) maternal heritability of diabetes/impaired fasting glucose and/or hearing impairment and/or maculopathy in three consecutive generations (or in two generations if 2 or 3 members of a family were affected). We sequenced the mtDNA in the 11 probands, in their mothers and in 80 controls. We identified 33 diabetes-suspected mutations, 1/33 was 3243A.G. Most patients (91%) and their mothers had mutations in complex I and/or IV of the respiratory chain. We measured the activity of these two enzymes and found that they were less active in mutated patients and their mothers than in the healthy control pool. The prevalence of hearing loss (36% vs 75–98%) and macular dystrophy (54% vs 86%) was lower in our mitochondrial diabetic adolescents than reported in adults. Moreover, we found a hitherto unknown association between mitochondrial diabetes and celiac disease. In conclusion, mitochondrial diabetes should be considered a complex syndrome with several phenotypic variants. Moreover, deafness is not an essential component of the disease in children. The whole mtDNA should be screened because the 3243A.G variant is not as frequent in children as in adults. In fact, 91% of our patients were mutated in the complex I and/or IV genes. The enzymatic assay may be a useful tool with which to confirm the pathogenic significance of detected variants

Mitochondrial Diabetes in Children: Seek and You Will Find It

Maternally Inherited Diabetes and Deafness (MIDD) is a rare form of diabetes due to defects in mitochondrial DNA (mtDNA). 3243 A>G is the mutation most frequently associated with this condition, but other mtDNA variants have been linked with a diabetic phenotype suggestive of MIDD. From 1989 to 2009, we clinically diagnosed mitochondrial diabetes in 11 diabetic children. Diagnosis was based on the presence of one or more of the following criteria: 1) maculopathy; 2) hearing impairment; 3) maternal heritability of diabetes/impaired fasting glucose and/or hearing impairment and/or maculopathy in three consecutive generations (or in two generations if 2 or 3 members of a family were affected). We sequenced the mtDNA in the 11 probands, in their mothers and in 80 controls. We identified 33 diabetes-suspected mutations, 1/33 was 3243A>G. Most patients (91%) and their mothers had mutations in complex I and/or IV of the respiratory chain. We measured the activity of these two enzymes and found that they were less active in mutated patients and their mothers than in the healthy control pool. The prevalence of hearing loss (36% vs 75–98%) and macular dystrophy (54% vs 86%) was lower in our mitochondrial diabetic adolescents than reported in adults. Moreover, we found a hitherto unknown association between mitochondrial diabetes and celiac disease. In conclusion, mitochondrial diabetes should be considered a complex syndrome with several phenotypic variants. Moreover, deafness is not an essential component of the disease in children. The whole mtDNA should be screened because the 3243A>G variant is not as frequent in children as in adults. In fact, 91% of our patients were mutated in the complex I and/or IV genes. The enzymatic assay may be a useful tool with which to confirm the pathogenic significance of detected variants

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