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Chaleur ou froid pour optimiser l’anabolisme?

22/11/2017 | Echauffement et blessures et Etudes Musculation

 

Plus d’anabolisme, moins de catabolisme avec…

Impact of local heating and cooling on skeletal muscle transcriptional response related to myogenesis and proteolysis
Roksana B. Zak European Journal of Applied Physiology October 2017

Purpose

To determine the impact of local muscle heating and cooling on myogenic and proteolytic gene responses following resistance exercise.

Methods

Recreationally trained males (n = 12), age 25.3 ± 1.5, % body fat 13.6 ± 1.92, completed four sets of 8–12 repetitions of unilateral leg press and leg extension while heating one leg, and cooling the other. Muscle biopsies were taken from the vastus lateralis of each leg pre and 4 h post exercise.

Results

MyoD, FOXO1, and MuRF1 mRNA increased with exercise regardless of temperature (p < 0.05). Myostatin, MYF5, and atrogin-1 mRNA decreased with exercise regardless of temperature (p < 0.05). Myogenin, MRF4, and CASP3 mRNA were higher in the hot condition, compared to the cold (p < 0.05). PAX7 mRNA was lower in the hot compared to cold condition (p = 0.041). FOXO3 mRNA was higher in the cold compared to hot condition (p = 0.037). AKT1 and AKT2 were unaffected by either exercise or temperature. Femoral artery blood flow volume was higher in the hot (375.2 ± 41.2 ml min− 1), compared to the cold condition (263.5 ± 23.9 ml min− 1), p = 0.01. Tissue oxygen saturation was higher in the hot (71.7 ± 4.8%) than cold condition (55.3 ± 5.0%).

Conclusion

These results suggest an impaired muscle growth response with local cold application compared to local heat application.

Les protéines laitières rapides ont un impact à court et à long terme sur la glycémie

05/11/2017 | Etudes sur les hormones et Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Cela explique que l’on peut ne pas le sentir au début puis y devenir sensible

Comparison between pre–exercise casein peptide and intact casein supplementation on glucose tolerance in high–fat diet–fed mice

Yutaka Matsunaga         Applied Physiology, Nutrition, and Metabolism, 2017

We hypothesized that along with exercise, casein peptide supplementation would have a higher impact on improving glucose tolerance than intact casein. Male six–week–old ICR mice were provided a high–fat diet to induce obesity and glucose intolerance. The mice were randomly divided into four treatment groups: control (Con), endurance training (Tr), endurance training with intact casein supplementation (Cas+Tr), and endurance training with casein peptide supplementation (CP+Tr). The mice in each group were orally administrated water, intact casein, or casein peptide (1.0 mg/g BW, everyday), and then subjected to endurance training (15–25 m/min, 60 min, 5 times/week for 4 weeks) on a motor–driven treadmill 30 min after ingestion. Our results revealed that total intra–abdominal fat was significantly lower in CP+Tr than in Con (p<0.05). Following an oral glucose tolerance test, the blood glucose area under the curve (AUC) was found to be significantly smaller for CP+Tr than for Con (p<0.05). Moreover, in the soleus muscle, GLUT4 protein levels were significantly higher in CP+Tr than in Con (p<0.01). However, intra–abdominal fat, blood glucose AUC, and GLUT4 protein content in the soleus muscle did not alter in Tr and Cas+Tr when compared with Con. These observations suggest that pre–exercise casein peptide supplementation has a higher effect on improving glucose tolerance than intact casein does in high–fat diet–fed mice.

L’acide férulique fait un comeback pour la prise de muscle

04/11/2017 | Etudes Compléments alimentaires et Etudes Anti-âge

 

Ferulic Acid Promotes Hypertrophic Growth of Fast Skeletal Muscle in Zebrafish Model
Ya We     Nutrients 2017, 9(10), 1066

As a widely distributed and natural existing antioxidant, ferulic acid and its functions have been extensively studied in recent decades. In the present study, hypertrophic growth of fast skeletal myofibers was observed in adult zebrafish after ferulic acid administration for 30 days, being reflected in increased body weight, body mass index (BMI), and muscle mass, along with an enlarged cross-sectional area of myofibers. qRT-PCR analyses demonstrated the up-regulation of relative mRNA expression levels of myogenic transcriptional factors (MyoD, myogenin and serum response factor (SRF)) and their target genes encoding sarcomeric unit proteins involved in muscular hypertrophy (skeletal alpha-actin, myosin heavy chain, tropomyosin, and troponin I). Western blot analyses detected a higher phosphorylated level of zTOR (zebrafish target of rapamycin), p70S6K, and 4E-BP1, which suggests an enhanced translation efficiency and protein synthesis capacity of fast skeletal muscle myofibers. These changes in transcription and translation finally converge and lead to higher protein contents in myofibers, as confirmed by elevated levels of myosin heavy chain (MyHC), and an increased muscle mass.

To the best of our knowledge, these findings have been reported for the first time in vivo and suggest potential applications of ferulic acid as functional food additives and dietary supplements owing to its ability to promote muscle growth.

Retour de la théorie de l’hyperplasie comme mode de croissance

18/08/2017 | Etudes Musculation

 

Differential requirement for satellite cells during overload-induced muscle hypertrophy in growing versus mature mice
Kevin A. Murach   Skelet Muscle. 2017; 7: 14.

Pax7+ satellite cells are required for skeletal muscle fiber growth during post-natal development in mice. Satellite cell-mediated myonuclear accretion also appears to persist into early adulthood. Given the important role of satellite cells during muscle development, we hypothesized that the necessity of satellite cells for adaptation to an imposed hypertrophic stimulus depends on maturational age.

Methods

Pax7CreER-R26RDTA mice were treated for 5 days with vehicle (satellite cell-replete, SC+) or tamoxifen (satellite cell-depleted, SC-) at 2 months (young) and 4 months (mature) of age. Following a 2-week washout, mice were subjected to sham surgery or 10 day synergist ablation overload of the plantaris (n = 6–9 per group). The surgical approach minimized regeneration, de novo fiber formation, and fiber splitting while promoting muscle fiber growth. Satellite cell density (Pax7+ cells/fiber), embryonic myosin heavy chain expression (eMyHC), and muscle fiber cross sectional area (CSA) were evaluated via immunohistochemistry. Myonuclei (myonuclei/100 mm) were counted on isolated single muscle fibers.

Results

Tamoxifen treatment depleted satellite cells by ≥90% and prevented myonuclear accretion with overload in young and mature mice (p < 0.05). Satellite cells did not recover in SC- mice after overload. Average muscle fiber CSA increased ~20% in young SC+ (p = 0.07), mature SC+ (p < 0.05), and mature SC- mice (p < 0.05). In contrast, muscle fiber hypertrophy was prevented in young SC- mice. Muscle fiber number increased only in mature mice after overload (p < 0.05), and eMyHC expression was variable, specifically in mature SC+ mice.

Conclusions

Reliance on satellite cells for overload-induced hypertrophy is dependent on maturational age, and global responses to overload differ in young versus mature mice.

Une supplémentation en corps cétoniques booste la récupération énergétique

17/08/2017 | Etudes cardio et Etudes Compléments alimentaires et Etudes Perte de poids

 

A Ketone Ester Drink Increases Postexercise Muscle Glycogen Synthesis in Humans
HOLDSWORTH, DAVID A         Medicine & Science in Sports & Exercise: September 2017 - Volume 49 - Issue 9 - p 1789–1795

Introduction: Physical endurance can be limited by muscle glycogen stores, in that glycogen depletion markedly reduces external work. During carbohydrate restriction, the liver synthesizes the ketone bodies, D-β-hydroxybutyrate, and acetoacetate from fatty acids. In animals and in the presence of glucose, D-β-hydroxybutyrate promotes insulin secretion and increases glycogen synthesis. Here we determined whether a dietary ketone ester, combined with plentiful glucose, can increase postexercise glycogen synthesis in human skeletal muscle.

Methods: After an interval-based glycogen depletion exercise protocol, 12 well-trained male athletes completed a randomized, three-arm, blinded crossover recovery study that consisted of consumption of either a taste-matched, zero-calorie control or a ketone monoester drink, followed by a 10-mM glucose clamp or saline infusion for 2 h. The three postexercise conditions were control drink then saline infusion, control drink then hyperglycemic clamp, or ketone ester drink then hyperglycemic clamp. Skeletal muscle glycogen content was determined in muscle biopsies of vastus lateralis taken before and after the 2-h clamps.

Results: The ketone ester drink increased blood D-β-hydroxybutyrate concentrations to a maximum of 5.3 versus 0.7 mM for the control drink (P < 0.0001). During the 2-h glucose clamps, insulin levels were twofold higher (31 vs 16 mU·L−1, P < 0.01) and glucose uptake 32% faster (1.66 vs 1.26 g·kg−1, P < 0.001). The ketone drink increased by 61 g, the total glucose infused for 2 h, from 197 to 258 g, and muscle glycogen was 50% higher (246 vs 164 mmol glycosyl units per kilogram dry weight, P < 0.05) than after the control drink.

Conclusion: In the presence of constant high glucose concentrations, a ketone ester drink increased endogenous insulin levels, glucose uptake, and muscle glycogen synthesis.

Les insectes apportent moins de protéines que prévu

28/07/2017 | Etudes Compléments alimentaires

 

Logique vu qu’une grande part de leur protéines (carapace et autres) sont complètement indigestibles

The high level of protein content reported in insects for food and feed is overestimated
Journal of Food Composition and Analysis Volume 62, September 2017, Pages 184-188


Highlights
• Insects have a great potential as future source for proteins.
• Total N is generally determined by Kjeldahl method.
• The N content in the cuticle errs the results.
• We propose to evaluate N derived from non-fibrous sources.
• It should result in an N-conversion factor similar among insects.

The potential of insects as a source of protein for future food and feed is widely admitted in the last couple years and is the object of numerous studies. The Kjeldahl method is widely used to quantify the crude protein content of insects which ranges from 8 to 70% of dry mass. This procedure evaluates the total concentration of Nitrogen (N), which is converted to protein by multiplying it by the nitrogen-to-protein conversion factor (N-factor) for meat (6.25).

Giving that the insect cuticle contents large amounts of fibrous chitin, a polysaccharide rich in N, and proteins tightly embedded in its matrix, and is not digested by humans or domesticated animals, using the Kjeldahl method overestimates the digestible protein content of insects. We propose to evaluate digetible nitrogen by quantifying N in the cuticle and sustraiting it from the total nitrogen content, and to calculate a new N-conversion factor which should be similar for all the insects species and their development stages.

Rôle de l’entraînement sur la densité mitochondriale

09/06/2017 | Etudes cardio et Etudes Perte de poids

 

Exercise training increases skeletal muscle mitochondrial volume density by enlargement of existing mitochondria and not de novo biogenesis
Anne-Kristine Meinild Lundby       Acta physiol 2017

Aims

1) determine whether exercise induced increases in muscle mitochondrial volume density (MitoVD) is related to enlargement of existing mitochondria or de novo biogenesis, 2) establish if measures of mitochondrial-specific enzymatic activities are valid biomarkers for exercise induced increases in MitoVD.
Method

Skeletal muscle samples were collected from twenty-one healthy males prior to and following 6 weeks of endurance training. Transmission electron microscopy was used for estimation of mitochondrial densities and profiles. Biochemical assays, western blotting and high resolution respirometry were applied to detect changes in specific mitochondrial functions.
Result

MitoVD increased with 55 ± 9% (P

< 0.001), whereas the number of mitochondrial profiles per area of skeletal muscle remained unchanged following training

. Citrate synthase activity (CS) increased (44 ± 12%, P < 0.001) however, there were no functional changes in oxidative phosphorylation capacity (OXPHOS, CI+IIP) or cytochrome c oxidase (COX) activity. Correlations were found between MitoVD and CS (P=0.01; r=0.58), OXPHOS, CI+CIIP (P=0.01; R=0.58) and COX (P=0.02; R=0.52) before training, after training a correlation was found between MitoVD and CS activity only (P=0.04; R=0.49). Intrinsic respiratory capacities decreased (P < 0.05) with training when respiration was normalized to MitoVD. This was not the case when normalized to CS activity although the percentage change was comparable.
Conclusions

MitoVD was increased by inducing mitochondrial enlargement rather than de novo biogenesis. CS activity may be appropriate to track training induced changes in MitoVD.

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