Diurnal Variations of Plasma Homocysteine,Total Antioxidant Status,and Biological Markers of Muscle Injury During Repeated Sprint: Effect on Performance and Muscle Fatigue—A Pilot Study

The aim of this study was (i) to evaluate whether homocysteine (Hcy), total antioxidant status (TAS), and biological markers of muscle injury would be affected by time of day (TOD) in football players and (ii) to establish a relationship between diurnal variation of these biomarkers and the daytime rhythm of power and muscle fatigue during repeated sprint ability (RSA) exercise. In counterbalanced order, 12 football (soccer) players performed an RSA test (5?×?[6 s of maximal cycling sprint?+?24 s of rest]) on two different occasions: 07:00–08:30?h and 17:00–18:30?h. Fasting blood samples were collected from a forearm vein before and 3–5?min after each RSA test. Core temperature, rating of perceived exertion, and performances (i.e., Sprint 1, Sprint 2, and power decrease) during the RSA test were significantly higher at 17:00 than 07:00?h (p?<?.001, p?<?.05, and p?<?.05, respectively). The results also showed significant diurnal variation of resting Hcy levels and all biological markers of muscle injury with acrophases (peak times) observed at 17:00?h. These fluctuations persisted after the RSA test. However, biomarkers of antioxidant status' resting levels (i.e., total antioxidant status, uric acid, and total bilirubin) were higher in the morning. This TOD effect was suppressed after exercise for TAS and uric acid. In conclusion, the present study confirms diurnal variation of Hcy, selected biological markers of cellular damage, and antioxidant status in young football players. Also, the higher performances and muscle fatigue showed in the evening during RSA exercise might be due to higher levels of biological markers of muscle injury and lower antioxidant status at this TOD. (Author correspondence: n_souissi@yahoo.fr)     

Influence of Chlorella powder intake during swimming stress in mice

We used the forced swimming test to investigate the influence of Chlorella powder intake during muscle stress training in mice. After day 14, swimming time was about 2-fold longer for Chlorella intake mice than for control swimming mice. Microarray analysis revealed that the global gene expression profile of muscle from the Chlorella intake mice was similar to that of muscle from the intact (non-swimming) mice, and the profile of these two groups differed from that of the control (swimming) mice. Gene ontology and pathway analyses of gene expression data showed that oxidoreductase activity and the leukotriene synthesis pathway were repressed in the Chlorella intake mice following the swimming test. In addition, measurements of free fatty acids, glucose, triglycerides, and lactic acid in the blood of Chlorella intake mice were higher than that of control mice. These findings suggest that metabolism in tissues is altered by Chlorella intake.     

Time‐of‐Day Effects on Myoelectric and Mechanical Properties of Muscle During Maximal and Prolonged Isokinetic Exercise

The aim of this study was to examine the time‐of‐day (TOD) effects in myoelectric and mechanical properties of muscle during a maximal and prolonged isokinetic exercise. Twelve male subjects were asked to perform 50 maximal voluntary contractions (MVC) of the knee extensor muscles at a constant angular velocity of 2.09 rad · sec^?1, at 06∶00 and 18∶00 h. Torque and electromyographic (EMG) parameters were recorded for each contraction, and the ratio between these values was calculated to evaluate variations of the neuromuscular efficiency (NME) with fatigue and with TOD. The results indicated that maximal torque values (T₄₅Max) was significantly higher (7.73%) in the evening than in the morning (p<0.003). The diurnal variation in torque decrease was used to define two phases. During the first phase (1st to the 26th repetition), torque values decreased fast and values were higher in the evening than in the morning, and during the second phase (27th to the 50th repetition), torque decreased slightly and reached a floor value that appeared constant with TOD. The EMG parameters (Root Mean Square; RMS) were modified with fatigue, but were not TOD dependent. The NME decrease–significantly with fatigue, showing that peripheral factors were mainly involved in the torque decrease. Furthermore, NME decrease was greater at 18∶00 than at 06∶00 h for the vastus medialis (p<0.05) and the vastus lateralis muscles (p<0.002), and this occurred during the first fatigue phase of the exercise. In conclusion, the diurnal variation of the muscle fatigue observed during a maximal and prolonged isokinetic exercise seems to reflect on the muscle, with a greater contractile capacity but a higher fatigability in the evening compared to the morning.     

Coordinated increase in albumin, fibrinogen, and muscle protein synthesis during hemodialysis: role of cytokines

Serum albumin, fibrinogen levels, and lean body mass are important predictors of outcome in end-stage renal disease (ESRD). We estimated the fractional synthesis rates of albumin (FSR-A), fibrinogen (FSR-F), and muscle protein (FSR-M) in nine ESRD patients and eight controls, using primed constant infusion of l-[ring-(13)C(6)]phenylalanine. Cytokine profile and arteriovenous balance of amino acids were also measured. ESRD patients were studied before (Pre-HD) and during hemodialysis (HD). Plasma IL-6, IL-10, and C-reactive protein increased significantly during HD. Despite a decrease in the delivery of amino acids to the leg, the outflow of the amino acids increased during HD. The net balance of amino acids became more negative during HD, indicating release from the muscle. HD increased leg muscle protein synthesis (45%) and catabolism (108%) but decreased whole body proteolysis (15%). FSR-A during HD (9.7 +/- 0.9%/day) was higher than pre-HD (6.5 +/- 0.9%/day) and controls (5.8 +/- 0.5%/day, P < 0.01). FSR-F increased during HD (19.7 +/- 2.6%/day vs. 11.8 +/- 0.6%/day, P < 0.01), but it was not significantly different from that of controls (14.4 +/- 1.4%/day). FSR-M intradialysis (1.77 +/- 0.19%/day) was higher than pre-HD (1.21 +/- 0.25%/day) and controls (1.30 +/- 0.32%/day, P < 0.001). Pre-HD FSR-A, FSR-F, and FSR-M values were comparable to those of controls. There was a significant and positive correlation between plasma IL-6 and the FSRs. Thus, in ESRD patients without metabolic acidosis, the fractional synthesis rates of albumin, fibrinogen, and muscle protein are not decreased pre-HD. However, HD increases the synthesis of albumin, fibrinogen, and muscle protein. The coordinated increase in the FSRs is facilitated by constant delivery of amino acids derived from the muscle catabolism and intradialytic increase in IL-6.     

Effects of energy or protein restriction followed by realimentation on the composition of gain and meat quality characteristics of Musculus longissimus dorsi in pigs

The effect of realimentation of fattening pigs on gain composition and intramuscular fat content in the longissimus dorsi muscle and their relationship to meat tenderness was investigated in 60 gilts. From day 90 to 168 of age, Group C (control) was fed according to the requirements, while from day 90 to 118 of age, Group R was fed restrictively (protein and energy) and Group P was fed restrictively with protein alone. This period was followed by adequate feeding. Comparative slaughter techniques were used; animals were slaughtered at the beginning of the study (day 90), at the end of the restriction period (day 118), and after two periods of realimentation (day 146 and day 168). Interactions between experimental treatments indicated that muscle protein gain (p < 0.05), muscle fat gain (p < 0.01), and shear force (p < 0.01) differed depending on period of realimentation. Muscle protein deposition differed only during the second period of realimentation, where Group R deposited more protein compared with Groups C and P (6.0, 4.5 and 5.0 g/d, respectively). Muscle fat deposition during the first period of realimentation was lower in Groups R and P than in Group C (0.73, 0.74 and 1.20 g/d, respectively) while in the second period Group R deposited considerably more fat than Groups C and P (2.39, 1.20 and 1.23 g/d, respectively). At the end of the first period, the shear force of Groups R and P was lower when compared with Group C (2.44, 2.79 and 3.22 kg, respectively); however, at final age it did not differ between treatments.     

Metabolic changes associated with sustained 48-Hr shivering thermogenesis in the newborn pig

Metabolic changes associated with sustained 48-hr shivering thermogenesis were studied in piglets maintained at 34 (thermoneutrality) or 25°C (cold) between 6 and 54 hr of life. Despite their high shivering activity and elevated heat production, cold-exposed piglets exhibited a slightly lower rectal temperature than thermoneutral animals (-1.1°C; P < 0.01) at the end of the treatment. The enhancement of heat production and shivering activity were associated with a decrease in muscle glycogen (− 47%; P < 0.05) and total lipid content (− 23%; P < 0.05), a reduction of blood lactate levels (P < 0.05) and an enhancement of muscle cytochrome oxidase activity (+20%;P < 0.05), which suggests that muscle oxidative potential was increased by cold exposure. Potential for capturing lipids (lipoprotein lipase activity) was also higher in the redrhomboideus muscle (+ 71%; P < 0.01) and lower in adipose tissue (−58%; P < 0.01) of the cold-exposed piglets. Measurements performed at the mitochondrial level show no changes inrhomboideus muscle, but respiratory capacities (state IV and FCCP-stimulated respiration) and intermyofibrillar mitochondria oxidative and phosphorylative (creatine kinase activity) capacities were enhanced inlongissimus dorsi muscle (P < 0.05). These changes may contribute to provide muscles with nonlimiting amount of readily oxidable substrates and ATP necessary for shivering thermogenesis. A rise in plasma norepinephrine levels was also observed during the second day of cold exposure (P < 0.05).     

Gender Differences in Lipoprotein Lipase Activity after Acute Exercise

Objective: To determine whether gender differences exist in lipoprotein lipase (LPL) activity in response to exercise and/or insulin. Exercise and insulin are known modulators of LPL activity in men, but this is less clear in women. LPL activity may predict propensity for obesity; therefore, understanding its modulators is of considerable importance. Research Methods and Procedures: Gender differences in skeletal muscle and adipose tissue LPL activity were determined after a single bout of exercise followed by a hyperinsulinemic/euglycemic clamp and compared with an identical rest day in healthy lean men (n = 10) and women (n = 10). Muscle and adipose tissue biopsies were obtained pre‐ (post‐exercise vs. rest) and post‐clamp. Results: Basal levels of muscle and adipose tissue LPL activity were not different between men and women. There was, however, a significant gender by day interaction for muscle LPL activity (p = 0.023) and adipose tissue LPL activity (p = 0.013). In muscle, this was because of a significant increase in LPL activity on the exercise vs. rest day in men (p < 0.001) but not women. Adipose tissue LPL activity also increased significantly in men on the exercise day relative to rest day (p = 0.04) but decreased in women (p = 0.10). The hyperinulinemic/euglycemic clamp had no independent effect on tissue LPL activity, in either gender, after rest or exercise. Discussion: In the 3 to 4 hours after exercise, muscle and adipose tissue LPL activity increased significantly in men, whereas LPL activity remained unchanged in women.     

Real-time polymerase chain reaction, in situ hybridization and immunohistochemical localization of insulin-like growth factor-I and myostatin during development of Dicentrarchus labrax (Pisces: Osteichthyes)

The distribution of insulin-like growth factor-I (IGF-I) and myostatin (MSTN) was investigated in sea bass (Dicentrarchus labrax) by real-time polymerase chain reaction (PCR), in situ hybridization (ISH) and immunohistochemistry. Real-time PCR indicated that IGF-I mRNA increased from the second day post-hatching and that this trend became significant from day 4. ISH confirmed a strong IGF-I mRNA expression from the first week post-hatching, with the most abundant expression being detected in the liver of larvae and adults. Real-time PCR also showed that the level of MSTN mRNA increased significantly from day 25. The expression of MSTN mRNA was higher in muscle and almost absent in other anatomical regions in both larvae and adults. Interestingly, the lateral muscle showed a quantitative differential expression of IGF-I and MSTN mRNAs in red and white muscle, depending on the developmental stage examined. IGF-I immunoreactivity was detected in developing intestine at hatching and in skeletal muscle, skin and yolk sac. MSTN immunostaining was evident in several tissues and organs in both larvae and adults. Both IGF-I and MSTN proteins were detected in the liver from day 4 post-hatching and, subsequently, in the kidney and heart muscle from day 10. Our results suggest, on the basis of a combined methodological approach, that IGF-I and MSTN are involved in the regulation of somatic growth in the sea bass. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. This research was supported by grants from the Italian Ministero dell’Università e della Ricerca Scientifica e Tecnologica (MIUR) and by the University of Padua (Progetto di Ateneo).     

Molecular mechanism underlying muscle mass retention in hibernating bats: Role of periodic arousal

Hibernators like bats show only marginal muscle atrophy during prolonged hibernation. The current study was designed to test the hypothesis that hibernators use periodic arousal to increase protein anabolism that compensates for the continuous muscle proteolysis during disuse. To test this hypothesis, we investigated the effects of 3‐month hibernation (HB) and 7‐day post‐arousal torpor (TP) followed by re‐arousal (RA) on signaling activities in the pectoral muscles of summer‐active (SA) and dormant Murina leucogaster bats. The bats did not lose muscle mass relative to body mass during the HB or TP‐to‐RA period. For the first 30‐min following arousal, the peak amplitude and frequency of electromyographic spikes increased 3.1‐ and 1.4‐fold, respectively, indicating massive myofiber recruitment and elevated motor signaling during shivering. Immunoblot analyses of whole‐tissue lysates revealed several principal outcomes: (1) for the 3‐month HB, the phosphorylation levels of Akt1 (p‐Akt1) and p‐mTOR decreased significantly compared to SA bats, but p‐FoxO1 levels remained unaltered; (2) for the TP‐to‐RA period, p‐Akt1 and p‐FoxO1 varied little, while p‐mTOR showed biphasic oscillation; (3) proteolytic signals (i.e., atrogin‐1, MuRF1, Skp2 and calpain‐1) remained constant during the HB and TP‐to‐RA period. These results suggest that the resistive properties of torpid bat muscle against atrophy might be attained primarily by relatively constant proteolysis in combination with oscillatory anabolic activity (e.g., p‐mTOR) corresponding to the frequency of arousals occurring throughout hibernation. J. Cell. Physiol. 222: 313–319, 2010. © 2009 Wiley‐Liss, Inc.     

Molecular characterization,expression patterns and subcellular localization of Myotrophin (MTPN) gene in porcine skeletal muscle

Myotrophin (MTPN) is an effective growth factor in promoting skeletal muscle growth in vitro and vivo and has been purified from porcine skeletal muscle. However, in pigs, the information on MTPN gene is very limited. In this study, we cloned cDNA sequences and analyzed the genomic structure of porcine MTPN gene. The deduced amino acid sequence of porcine MTPN contains two the ankyrin repeat domains. RT-PCR analysis revealed that porcine MTPN gene was widely expressed in many tissues, a high expression level was observed in the spleen, liver and uterus, and transient transfection indicated that porcine MTPN proteins was located in cytoplasms within Pig Kidney Epithelial cells (PK15). Quantitative real-time PCR (qRT-PCR) analyses showed that MTPN expression peaked at embryonic 65 day post conception (dpc). During postnatal muscle development, MTPN expression was down-regulated from the 3 day to the 180 day in Yorkshire pigs. This result suggests that the MTPN gene may be important gene for skeletal muscle growth and provides useful information for further studies on its roles in porcine skeletal muscle.     

Seasonal variation in body composition in an Afrotropical passerine bird: increases in pectoral muscle mass are,unexpectedly, associated with lower thermogenic capacity

Phenotypic flexibility in avian metabolic rates and body composition have been well-studied in high-latitude species, which typically increase basal metabolic rate (BMR) and summit metabolism (M_sum) when acclimatized to winter conditions. Patterns of seasonal metabolic acclimatization are more variable in lower-latitude birds that experience milder winters, with fewer studies investigating adjustments in avian organ and muscle masses in the context of metabolic flexibility in these regions. We quantified seasonal variation (summer vs winter) in the masses of organs and muscles frequently associated with changes in BMR (gizzard, intestines and liver) and M_sum (heart and pectoral muscles), in white-browed sparrow-weavers (Plocepasser mahali). We also measured pectoral muscle thickness using a portable ultrasound system to determine whether we could non-lethally estimate muscle size. A concurrent study measured seasonal changes in BMR and M_sum in the same population of sparrow-weavers, but different individuals. There was no seasonal variation in the dry masses of the gizzard, intestines or liver of sparrow-weavers, and during the same period, BMR did not vary seasonally. We found significantly higher heart (~ 18% higher) and pectoral muscle (~ 9% higher) dry mass during winter, although ultrasound measurements did not detect seasonal changes in pectoral muscle size. Despite winter increases in pectoral muscle mass, M_sum was ~ 26% lower in winter compared to summer. To the best of our knowledge, this is the first study to report an increase in avian pectoral muscle mass but a concomitant decrease in thermogenic capacity.

     

Proliferation and differentiation of androgenetic cells in fetal mouse chimeras

The properties of androgenetic cells and their ability to proliferate and differentiate were examined in post-midgestation chimeras. In several tissues, namely the brain, cardiac muscle, skeletal muscle and intestinal epithelium, the rate of proliferation of androgenetic cells was higher than that of normal cells in day 13 embryos. This higher rate of proliferation was however less pronounced by day 17–18 of development. It is possible that IGF2, a major growth factor regulating fetal growth, could play a role in the increased proliferation of androgenetic cells. Igf2 is also an imprinted gene that is expressed only when inherited paternally. Indeed, in the smooth muscle, cartilage and intestinal epithelium, patches of androgenetic (ag) cells exhibited higher levels of IGF2 mRNA than neighbouring wild-type cells. Surprisingly, we also detected expression of Igf2 in ag cells of ectodermal origin; this gene is not normally expressed in this lineage. This expression was observed in the brain, epidermis and in the epithelium of the tongue. We attempted to confirm the identity and differentiation status of ag cells with the help of cell-type specific antibodies and lectins. Evidence for only one of the cell types analysed, i.e. the goblet cells of the gut, suggests a delay or aberrant differentiation of ag cells.     

Fasting and refeeding in carp,Cyprinus carpio L.: the mobilization of reserves and plasma metabolite and hormone variations

Summary Carp, Cyprinus carpio, were subjected to a short term of fasting (2 months) and 12 days of refeeding. The early changes produced in plasma metabolites and hormones (insulin and glucagon) and their respective energy contribution in liver and muscle during fasting and refeeding was studied. Two phases of fasting were differentiated. The first phase (until day 8 of fasting) was characterized by a reduction in the hepatosomatic index mainly due to glycogen mobilization. A transitory increase in plasma glucose and lactate suggested an initial increase in energy demand. No changes were produced in the percentage of glycogen and protein in muscle, but musculosomatic index and the total body muscle protein decreased. Although the most depleted tissue in this phase was the liver, the loss of energy content of total muscle was higher. Stabilization of liver glycogen content, plasma glucose and lactate levels, decreased muscle protein levels and a reduction in the rate of body weight loss characterized the second phase (from day 8 of fasting). Protein content in whole muscle decreased by 22%, similar to the first phase. The energy expenditure of both liver and muscle was lower in this phase. Plasma insulin levels decreased two-fold and plasma glucagon three-fold in the first phase and remained low in the second phase of fasting. Twelve days of refeeding produced a greater increase in daily growth rate than in the control group and a recovery of plasma insulin, glucagon and glucose levels. Liver completely recovered. In contrast, musculosomatic index, protein and lipid content indicated that muscle did not completely recover from the 2 months of fasting, although and overshoot of muscle glycogen was observed.Abbreviations ANOVA analysis of variance - bw body weight - D1, D2, D5, D8, D19, D50 1, 2, 5, 8, 19 and 50 days of fasting, respectively - GSI gonadosomatic index - HSI hepatosomatic index - MSI musculosomatic index - P-DNA deoxyribonucleic acid phosphorus     

Changes in the content of glycogen and its metabolites during acute exposure ofAnabas testudineus (Bloch) to furadan

Significant differences were observed in glycogen metabolism ofAnabas testudineus exposed to an acute lethal (1.56 mg/litre) and a sublethal (0.56 mg/litre) concentration of furadan. At sublethal concentration, the muscle glycogen which was utilized during the early periods of exposure, was replenished in the later period of exposure and at 120 h, the muscle glycogen levels were higher than the control. At higher concentration, the liver glycogen levels showed an increase presumably at the expense of fuel reserves of the muscle.     

Growth and body composition of rohu, Labeo rohita (Hamilton), fed compound diet: winter feeding and rearing to marketable size

A 122‐day growth trial was conducted to observe the impact of polyhouse in winter on growth, conversion efficiencies and body composition of fingerling Labeo rohita (7.9 ± 1.1 cm; 4.60 ± 0.18 g). Fish were stocked (1.5 m^?2) in polyhouse and outdoor concrete tanks (250 m²) in duplicate and fed a compound diet [35% crude protein (CP)] to apparent satiation twice daily, at 09.00 and 17.00 hours. A natural photoperiod was maintained during the trials. At the end of the trials, polyhouse‐reared fish produced significantly (P < 0.01) higher values for weight increment, specific growth rate (SGR %), protein efficiency rate (PER), protein productive value (PPV) and better feed conversion ratio (FCR). Polyhouse‐reared fish showed higher (P < 0.01) CP and fat, and lower (P < 0.01) moisture and ash contents in the muscle. In the second part of the study, which also lasted 122 days, polyhouse‐reared young L. rohita (21.7 ± 1.3 cm; 127.8 ± 0.69 g) were raised to marketable size in outdoor earthen ponds (500 m²) at a stocking density of 0.37 m^?2 to examine the effects of feeding traditional feed mixture and compound diet (30% CP) on growth and body composition of fish. Labeo rohita fed the compound diet showed higher (P < 0.01) values for weight increment, SGR (%), PER and PPV, and better (P < 0.01) FCR than those fed traditional feed. Proximate composition of fish muscle showed higher (P < 0.05) CP and fat, and lower (P < 0.05) moisture and ash contents in fish fed the compound diet. The results suggest that polyhouse may be used successfully to culture L. rohita during winter, and that thereafter the fish may be reared in earthen ponds using the compound diet to obtain better production.     

Induction of Oxidatively Modified Proteins in Skeletal Muscle by Electrical Stimulation and Its Suppression by Dietary Supplementation of (-)-Epigallocatechin Gallate

The oxidative stress produced by electrical stimulation-induced muscle contraction was examined in the skeletal muscle proteins of rats that had been fed on the dietary flavonoid, (-)-epigallocatechin gallate (EGCg). Electrical stimulation of the rat leg muscle every second day for a two-week period resulted in an increased (p<0.05) muscle weight and accumulation of oxidatively induced modified proteins. Similar stimulation conducted every day for only one week had no effect on the muscle weight or protein oxidation, although the rate of protein degradation increased. Rats fed on a 20% casein diet supplemented with 0.1% EGCg for 2 weeks responded to the electrical stimulation of muscle contraction by reducing the increased muscle protein carbonyl content when compared to their counterparts fed on a control diet. There was no change in activity of antioxidative enzymes in muscle tissue of the EGCg-fed rats receiving electrical stimulation. The results of this study show that the antioxidative property of EGCg was effective for suppressing oxidative modification of the skeletal muscle protein induced by electrical stimulation. This finding demonstrates that EGCg has a beneficial effect in vivo on the free radical-mediated oxidative damage to muscle proteins.