[The role of mTOR in the regulation of skeletal muscle metabolism].

mTOR enzyme belongs to a family of specific serine/threonine protein kinases. mTOR plays an important role in the transmission of extracellular signals by phosphorylation of various substrates in many metabolic reactions in humans. Protein mTOR, having protein kinase activity, is encoded by a gene FRAP1, which is localized on chromosome 1 (1p36.2) in skeletal muscle. It exists in two mTOR protein complexes mTORC1 and mTORC2 with various sensitivity to the inhibitory effect of rapamycin. mTOR regulates metabolism in skeletal muscle by phosphorylation of various of protein metabolizing enzymes as well as transcription and translation factors. mTOR expression occurs in response to metabolic requests of muscles and leads to increased metabolism of proteins. The data of recent studies suggest an important role of mTOR in the regulation of intracellular metabolism and point to the need of studying the molecular mechanisms involved in physiological function of skeletal muscles.

The ACTN3 R577X polymorphism in Russian endurance athletes.

OBJECTIVE: The functional 577R allele of the alpha-actinin-3 (ACTN3) gene has been reported to be associated with elite power athlete status, while the nonfunctional 577XX genotype (predicts an alpha-actinin-3 deficient phenotype) has been hypothesised as providing some sort of advantage for endurance athletes. In the present study, the distribution of ACTN3 genotypes and alleles in Russian endurance-oriented athletes were examined and association between ACTN3 genotypes and the competition results of rowers were sought. METHODS: 456 Russian endurance-oriented athletes of regional or national competitive standard were involved in the study. ACTN3 genotype and allele frequencies were compared with 1211 controls. The data from the Russian Cup Rowing Tournament were used to search for possible association between the ACTN3 genotype and the long-distance (approximately 6 km) rowing results of 54 athletes. DNA was extracted from mouthwash samples. Genotyping for the R577X variant was performed by PCR and restriction enzyme digestion. RESULTS: The frequencies of the ACTN3 577XX genotype (5.7% vs 14.5%; p<0.0001) and 577X allele (33.2% vs 39.0%; p = 0.0025) were significantly lower in endurance-oriented athletes compared with the controls, and none of the highly elite athletes had the 577XX genotype. Furthermore, male rowers with ACTN3 577RR genotype showed better results (1339 (11) s) in long-distance rowing than carriers of 577RX (1386 (12) s) or 577XX (1402 (10) s) genotypes (p = 0.016). CONCLUSION: Our data show that the ACTN3 577X allele is under-represented in Russian endurance athletes and is associated with the rowers' competition results.

[Association of the mitochondrial transcription factor (TFAM) gene polymorphism with physical performance of athletes].

The aim of the study was to investigate allelic distribution of the mitochondrial transcription factor gene (TFAM) Ser12Thr polymorphism in athletes (n = 1537) and controls (n = 1113), and to find interrelation between genotypes and aerobic capacity in rowers (n = 90). Genotyping was performed by restriction fragment length polymorphism analysis. Aerobic capacity (maximal oxygen consumption (VO2max) and maximal power production capacity (Wmax)) was determined using an incremental test to exhaustion by rower ergometer. The frequency of TFAM 12Thr allele was significantly higher in endurance-oriented athletes (n = 588) than in controls (14.0% vs. 9.1%; p <0.0001), and increased with the growth of skills. Furthermore, TFAM 12Thr allele was associated with high values of aerobic performance (when Wmax and VO2max were measured). Thus, TFAM gene Ser12Thr polymorphism is associated with physical performance of athletes.

[Association of PPARD gene polymorphism with human physical performance].

Peroxisome proliferator-activated receptor delta (PPARdelta) regulates expression of genes involved in lipid and carbohydrate metabolism. To examine the association of a functional +294T/C polymorphism of PPARD gene with human physical performance, we have studied the distribution of PPARD alleles and genotypes in a cohort of athletes (n=1256; stratified by specialty and skill level) and controls (n=610). We found that the frequency of PPARD C allele (with higher transcriptional activity compared to T allele) in a group of endurance-oriented athletes (n=898) is significantly higher than in controls (18.3% vs. 12.1%; p < 0.0001). Moreover, in the group of endurance-oriented athletes with cyclic activity we revealed an increasing frequency of PPARD C allele with the rising of athletes' skill level. Thus, PPARD C allele is associated with predisposition to endurance performance.

[SIGNALING PATHWAYS INVOLVED IN THE REGULATION OF PROTEIN METABOLISM IN SKELETAL MUSCLE].

The ability of muscle cells to respond to certain signaling molecules depends on the presence of specific proteins-receptors, ion channels and transporters, which create a system of metabolic inputs. All cells in the human body have a transmembrane signaling system that allows to get information from extracellular stimuli such as hormones, neurotransmitters, proteins, peptides, derivatives of amino acids and fat acids, sensor molecules. The results of researches published in the last two years, which expand knowledge of action of various factors on protein metabolism in skeletal muscles are presented in the review. The main attention is turned to the discovery and expansion of signaling pathways involved in the regulation of protein metabolism in skeletal muscle in different functional states of the person.

[THE ROLE OF microRNAs IN THE REGULATION OF MUSCLE METABOLTSM].

MicroRNAs, class of the small RNA containing approximately 22 nucleotides take part in regulation of metabolism of skeletal muscles as enzymes, hormones and transcription factors. They are able to regulate the intensity of the translation process through complementary. interaction with mRNA. The review presents the results of studies published in the last two years, which increase the knowledge of the effects of microRNAs on the key stages of protein synthesis in skeletal muscle. The main attention is paid to achievements which open and specify a microRNA role in regulation of the signaling pathways that coordinate intracellular metabolism of skeletal muscles at different finctionni onneiilinnc nf then

The angiotensin converting enzyme I/D polymorphism in Russian athletes.

The deletion (D) allele of the human ACE gene is associated with higher ACE activity than the insertion (I) allele. There is controversy as to whether the ACE genotype may be associated with elite athletic status; recent studies have identified no significant associations amongst those drawn from mixed sporting disciplines. However, such lack of association may reflect the mixed nature of such cohorts, given that an excess frequency of the I allele has been reported amongst elite endurance athletes, and an excess of the D allele amongst those engaged in more power-orientated sports. We examined this hypothesis by determining ACE I/D allele frequency amongst 217 Russian athletes (swimmers, skiers, triathletes and track-and-field participants) prospectively stratified by performance ('outstanding' or 'average'), and the duration of their event (SDA (<1 min), MDA (1 to 20 min), and LDA (>20 min): short, middle and long distance athletes respectively). ACE genotype and allele frequencies were compared to 449 controls. ACE genotype frequency amongst the whole cohort, or the outstanding athletes alone, was no different to that amongst sedentary controls. However, there was an excess of the D allele (frequency 0.72, P=0.001) amongst the outstanding SDA group, and an excess of the I allele (frequency 0.63, P=0.032) amongst the outstanding MDA group. These findings were replicated in the outstanding swimmers, with track and field SDA similarly demonstrating an excess of the D allele (P=0.01). There was no association found between the outstanding LDA and ACE genotype (P=0.27). These data not only confirm an excess of the D allele in elite SDA, and I allele in elite MDA, but also offer an explanation as to why any such association may be hard to detect amongst a heterogeneous cohort of mixed athletic ability and discipline.

Properties of free and occupied androgen receptor in rat skeletal muscle cytosol: effect of testosterone.

Our aim was to investigate the effect of a single testosterone (T) injection on the androgen receptor (AR) in rat skeletal muscle (SM) cytosol. The properties of AR were studied in order to establish the protocol for differential determination of free and hormone-occupied AR in SM cytosols from non-hormone-deficient animals. Using the developed ligand-exchange protocol, we demonstrated that injection of T (1 mg/kg) caused alternating changes of the total AR binding. The binding minimum (23% of the control) was measured 1 h after the injection. It was followed by pronounced and lasting elevation of the AR binding. In the control cytosols, AR complexes constituted approximately 25% of the total receptor content. Changes of their relative content immediately after T administration were consistent with rapid nuclear translocation of the AR. Inhibition of protein synthesis by cycloheximide (CHI) injection demonstrated that delayed and lasting increase of the AR binding after T injection partially depended on the stimulated protein synthesis. Altogether, the obtained evidence supports the assumption that the AR mediates elevation of its own gene expression in SM upon administration of T.

Dietary nutrient intake comparisons for rural and urban Russian boys, ages 6, 9, and 15 years, living in St. Petersburg and surrounding areas.

Dietary intake data were gathered on 123 rural and 111 urban males, ages 6, 9, and 15 years, living in and near St. Petersburg, Russia. Data were analyzed to estimate intakes of kilocalories, protein, calcium, iron, vitamin A, thiamin, riboflavin, niacin, vitamin C, and percentage of kilocalories from protein, carbohydrate, and fat. Comparisons were made between nutrient intakes of urban and rural subjects; intakes were also compared with the Recommended Dietary Intakes (RDI) of the USSR Research Institute of Nutrition. There were no significant differences between rural and urban boys in energy intake at any age. Urban boys consumed more vitamin C at ages 6 and 9, had higher intakes of protein, calcium, and niacin at age 9, and consumed more protein at age 15. Rural boys had higher intakes of riboflavin and calcium than urban boys at age 6. Urban boys consumed larger proportions of energy as carbohydrate at age 6, protein at age 9, and both protein and fat at age 15 than rural subjects. Rural boys had higher proportions of kilocalories from fat at age 6 and carbohydrate at age 15 than urban boys. Mean nutrient intakes below the RDI were: energy for rural boys at 9 and 15 years; iron for rural subjects at ages 6 and 9 and urban boys at age 6; calcium for rural and urban boys at all ages; vitamin C for rural subjects at ages 6 and 9; vitamin A for rural and urban boys at age 15; and protein for rural boys at age 15. At age 6, rural boys had nutrient intakes superior to those of urban boys; urban nutrient intakes were better than rural at ages 9 and 15. © 1994 Wiley-Liss, Inc.

Somatic comparisons of urban and rural Russian boys, ages 6, 9, and 15 years, living in St. Petersburg and surrounding areas.

Somatic data were collected during September 1991 on 280 males, ages 6, 9, and 15 years, residing in urban St. Petersburg, Russia, and in rural regions surrounding the city. Comparisons are made between urban and rural groups for measures of body size and form, skinfold thicknesses, body mass index (BMI), and estimated arm muscle area (ARM). The data were analyzed in 2 (urban-rural) × 3 (age) analyses of variance, with an alpha level of P < 0.05. Age differences were evident for all measurements. A significant main effect for urban-rural was found for stature, lower limb height, and calf girth; differences approached significance (P < 0.07) for body weight and sitting height. Urban children were larger than rural children in stature, sitting height, lower limb height, calf girth, and body weight. The interaction was nonsignificant. Urban and rural boys did not differ on measures of body form. Similar means were obtained for the sum of skinfolds, the BMI, and ARM in urban and rural boys. Compared with data collected more than a century ago, present-day 15-year-olds are 22 cm taller. It has often been suggested that living in an urban environment provides greater access to the amenities of life than living in a rural area. Although these amenities are difficult to observe differences do exist and the secular trend continues. © 1994 Wiley-Liss, Inc.

[Fluoroimmunologic analysis of proteins]. / Fluoroimmunnyi analiz belkov.

Review contains new data on protein fluoroimmunoassay (FIA), which combines advantages of RIA and EIA. Basic approaches to antibody production, principles of homogeneous and heterogeneous FIA as well as of time-resolved FIA properties of 28 fluorescent labels presenting various classes of organic compounds (of which most prospective are aminoquinolone, cyanocoumarines, chlorophylls, phycobiliproteins, metallorganic compounds) are described. Some examples of FIA application for quantitative evaluation of proteins in biological samples, properties of some FIA kits, and specifications of 6 fluorimeters developed for FIA are given. The nearest perspectives of FIA development and application in medical and biological research are considered.

[The role of phosphorylation and dephosphorylation of receptors in the regulation of steroid hormone binding]. / Rol' fosforilirovaniia i defosforilirovaniia retseptorov v reguliatsii sviazyvaniia steroidnykh gormonov.

Modern conceptions on the ways of possible modification of steroid hormones receptor proteins in cell and a functional significance of the given process are stated. Enzyme systems ensuring the reactions of receptor proteins phosphorylation and dephosphorylation are analyzed. Data on the ATP participation in the processes of receptor proteins phosphorylation and hormone-receptor complex activation are generalized. Participation of the phosphorylation-dephosphorylation processes of receptor proteins in the hormonal signal transfer in a cell is shown possible.

[The steroid hormone levels and receptors of steroid hormone receptors in rat muscles during physical exertion]. / Soderzhanie i retseptsiia steroidnykh gormonov v myshtsakh krys pri fizicheskikh nagruzkakh.

It is shown that the testosterone content in skeletal muscles of female albino rats is 2-fold decreased, while the estradiol content-1.5-fold increased and progesteron content showed no changes after systematic physical exercises. The pharmacokinetic investigations showed that androgen half-life in the organism decreased from 8 to 5 h under physical exercises. The amount of androgen receptors in cytosol of skeletal muscles increases from 1.34 +/- 0.08 to 1.71 +/- 0.10 fmol/mg per 1 mg of protein. Kd is 0.40 +/- 0.03 and 0.48 +/- 0.08 nM, respectively. Sensitivity of the organism to hormonal signal play an important role in the metabolism regulation in skeletal muscles along with the hormonal content change during the organism adaptation to physical exercises.

[Tropomyosin metabolism in muscles and its blood levels during physical exertion]. / Metabolizm tropomiozina v myshtsakh i ego soderzhanie v krovi pri fizicheskikh nagruzkakh.

Physical exercise induces phasic changes in the tropomyosin content and metabolism in muscles and its concentration in blood. The intensive catabolic processes (decrease of 14C-leicin inclusion and time of half-life) of muscle tropomyosin and its appearance in blood were shown 2-24 hours after the exercise. Intensive anabolic processes of muscle tropomyosin were found at the late period of rest (72-144 h). These results reveal the biochemical mechanism of muscle adaptation to physical exercise. Data on the tropomyosin content in blood permit recommending tropomyosin for development of the diagnostic test of functional condition of the skeletal muscle.

[Effect of cycloheximide on synthesis of skeletal muscle proteins and nuclear DNA-dependent RNA-polymerase activity]. / Sintez belkov skeletnykh myshts i DNK-zavisimiia RNK-polimeraznaia aktivnost' iader pri deistvii tsiklogeksimida.

A high sensitivity towards cycloheximide is shown for three main protein fractions of albino rat skeletal muscle, i. e. a 50% inhibition of myofibrillar protein synthesis is caused by a dose of 0.1 mg/100 g of body weight after 3.5 h, the rate of inhibition of two other fractions is even higher. A dose of 3.0 mg/100 g of body weight inhibits the synthesis of the sarcoplasmic and myofibrillar proteins by 96% by the end of the 15th minute. Administration of cycloheximide in vivo (0.3 mg/100 g of body weight) inhibits the alpha-amanitin-resistant DNA-dependent RNA-polymerase activity of the nuclei. The relation between the inhibition rate and time of the cycloheximide action is ruled by the first order kinetic. This allows postulating the existence of a fast renewal with a period of half-life of about 110 min (determined graphically) among nuclear proteins involved in the transcription of rRNA. The idea of this protein participation in adaptive shifts of rRNA synthesis in the systematic skeletal muscle function is suggested.

[The effect of physical exertion on the activity of calpains and myeloperoxidase level in skeletal muscles of rats]. / Vliianie fizicheskikh nagruzok na aktivnost' kalpainov i soderzhanie mieloperoksidazy v skeletnykh myshtsakh krys.

It has been established that the activity of calpains and the amount of neutrophil myeloperoxidase in skeletal muscles of rats increases after the 24-48 h-rest, that followed an intensive single physical exercise. Adaptation which appears as a result of systematic physical exercises causes less pronounced changes in the activity of proteolytic enzymes. Free ubiquitin content in skeletal muscles remains unchanged during training and in posttraining periods.

[Immunoradiometric analysis of rat myeloperoxidase]. / Immunoradiometricheskii analiz mieloperoksidazy krysy.

The immunoradiometric assay of rat myeloperoxidase (MPO) was developed based on the usage of the CNBr-activated sepharose as a solid phase for antiMPO and of [125I] IgG (the affinity preparation of antiMPO) as a label. The analysis lasted for 8 h and standard curve limits were 0.5-500 ng per tube. Intra and inter assay coefficients of variation did not exceed 3% and 6.5%, respectively. It was shown by the above method that the intensive swimming of male rats led to an increase in the MPO concentration in blood plasma and to its decrease in neutrophils.

[Radioimmunologic analysis of steroids. Scientific and practical aspects]. / Radioimmunologicheskii analiz steroidov. Nauchno-prakticheskie aspekty.

Many-year experience of using authors' own systems for steroid radioimmunoassay (RIA) is summarized. Synthesis of natural and anabolic steroid derivatives and their conjugation with bovine serum albumin are considered. Schemes of rabbits immunization with steroid-protein conjugates, and the antisera characteristics are described. Data on comparison of 3H- and 125I-ligands in steroid RIA are presented as well as the characteristics of the RIA systems. The RIA optimization and quality control problems as well as the prospects of the RIA development are discussed.

[Quantitative gas chromatographic determination of 3-methylhistidine in biological fluids]. / Kolichestvennyi gazokhromatograficheskii analiz 3-metilgistidina v biologicheskikh zhidkostiakh.

The gas chromatographic procedure is suggested to determine 3-methylhistidine in biological fluids. The amino acid fraction containing 3-methylhistidine is separated by ion-exchange chromatography. Amino acids are transformed into N-trifluoroacetyl-O-isobutyl esters which are analyzed by the gas chromatography instrument with micropacked columns and ionization-resonance detector. The limit of the quantitative determination of 3-methylhistidine is 50 ng per a probe.

[Radioimmunological assay of human lysozyme and effect of exertion on its blood level]. / Radioimmunologicheskii metod analiza lizotsima cheloveka i vliianie fizicheskoi nagruzki na ego soderzhanie v krovi.

Radioimmunoassay (RIA) of human lysozyme was developed using 125I-lysozyme and specific antiserum to the enzyme. Titre of antibodies produced in the antiserum was as high as 1:81,000, affinity constant constituted 1.3.10(9) M/L. Optimum patterns of the RIA were achieved under the following conditions: B0 = 50-55%, T = 25-30.10(3) cpm, BSA = 0.5%, NaCl = 0.85%, charcoal 2.5%. The antibody-antigen reaction was carried out within 30 min, 30 and 15 min at 37 degrees, 20 degrees and 4 degrees, respectively. The RIA enabled to estimate lysozyme with sensitivity of 0.25 ng/ml, while the standard curve was optimal within the range of 0.1-1.0 ng/tube. Intra- and inter-assay coefficients did not exceed 4% and 8%, respectively. Recovery of the standard lysozyme concentration was equal to 96.5 +/- +/- 0.8%. As shown by the RIA intensive physical exercises resulted in an increase of lysozyme content in blood, which appears to occur due to the enzyme secretion from phagocytes. Calculation of the secretion index may be used for evaluation of blood phagocytes functional state.