Cliquez sur les images pour acquérir mes livres : frais de port gratuits et envoi rapide.

Pour suivre mon actualité ou me contacter : sur Facebook.

Effets de l’exercice sur les concentrations de l’irisine

21/10/2016 | Etudes cardio et Etudes Musculation et Etudes Perte de poids et Etudes Anti-âge

 

Effets de l’exercice sur les concentrations de l’irisine circulatoire chez les adultes sains : revue générale
Science & Sports Volume 31, Issue 5, October 2016, Pages 251–260       A.C. Rodrigues

Objectifs

L’irisine est une myokine induite par l’exercice, responsable de la régulation de la protéine découplante 1 (UCP-1) dans le tissu adipeux beige. Cette étude vise à faire le point sur les effets d’exercice aigus et chroniques sur les concentrations circulantes d’irisine chez les adultes sains.

Informations

Nous avons réalisé, à partir des bases de données Medline et ScienceDirect, une revue de la littérature parue entre janvier 2012 et mars 2016, en utilisant les termes d’indexation suivants : irisine, exercice aigu, exercice chronique et entraînement. Pour les besoins de l’analyse, les études ont été divisés en exercice aigu et exercice chronique. Seize articles répondaient aux critères d’inclusion/exclusion, huit études portant sur l’exercice aigu, quatre avec l’exercice chronique et quatre avec les deux. Parmi les études portant sur l’exercice aigu, deux seulement n’ont pas observé d’augmentation des concentrations sériques et plasmatiques d’irisine après la séance d’exercice. L’exercice en résistance et l’exercice à haute intensité augmentaient davantage l’irisine que l’exercice aérobie et que l’exercice à faible d’intensité. Une seule étude a révélé une augmentation des concentrations circulantes d’irisine après plusieurs semaines d’entraînement en comparaison aux concentrations mesurées avant entraînement. Une autre étude a observé une augmentation des concentrations circulantes d’irisine dans le groupe entraîné par rapport au groupe témoin.

Conclusion

L’exercice aigu augmente les concentrations circulantes d’irisine. L’exercice en résistance et l’exercice à haute intensité augmentent davantage l’irisine. Par contre, un entraînement prolongé de plusieurs semaines ne semble pas modifier les concentrations circulantes d’irisine.

Urolithine B comme un nouveau régulateur de la masse musculaire

19/10/2016 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Identification de l’urolithine B comme un nouveau régulateur de la masse musculaire
Nutrition Clinique et Métabolisme Volume 30, Issue 3, September 2016, Pages 252         J. Rodriguez

Introduction et but de l’étude
Le muscle squelettique est le tissu le plus abondant du corps humain. Le contrôle de sa masse est essentiel pour assurer ses fonctions physiologiques comme la locomotion, la respiration ou encore la posture. Il joue également un rôle majeur dans le contrôle du métabolisme. L’atrophie musculaire est associée à une diminution de force, à des désordres métaboliques et à une mauvaise qualité de vie. Par conséquent, les stratégies nutritionnelles visant à atténuer la fonte musculaire liée à des conditions (patho) physiologiques représentent un intérêt thérapeutique majeur. Le but de cette étude est d’évaluer les effets de l’urolitine B, un métabolite des éllagitanins, sur le croissance et la fonte musculaire.

Matériel et méthodes
Des myotubes C2C12 ont été incubés 24 h en présence de 15 μM d’urolithine B. La croissance cellulaire, la synthèse et la dégradation protéiques ont été mesurées et les voies de signalisation associées ont été systématiquement étudiées. Afin d’évaluer in vivo les effets sur l’hypertrophie, des minipompes osmotiques délivrant de manière continue 10 μg d’urolithine B par jour pendant 28 jours ont été implantées à des souris. Les effets sur l’atrophie ont été étudiés après section du nerf sciatique et implantation de minipompes osmotiques (10 μg d’urolithine B, par jour, durant 3 ou 7 jours).

Résultats et analyse statistique
L’urolithine B stimule la croissance des myotubes (+ 40 %, p < 0,001), augmente la synthèse (+ 90 %, p < 0,001) et diminue la dégradation protéique (− 20 %, p < 0,001). L’analyse des voies de signalisation révèle une plus grande activité de la voie de mTORC1 et une inhibition du système ubiquitine–protéasome. Le récepteur aux androgènes semble impliqué puisque son inhibition par un siRNA ou un agent pharmacologique bloque totalement l’hypertrophie induite par l’urolithine B. Cette dernière stimule la croissance musculaire chez la souris en augmentant la synthèse des protéines (activité trois fois supérieure dans le muscle tibialis anterior) et réduit l’atrophie induite par une dénervation.

Conclusion
Nos résultats indiquent que l’urolithine B régule la masse musculaire probablement en agissant via le récepteur aux androgènes. Notre étude met ainsi en évidence l’utilité potentielle de l’urolithine B dans le traitement de l’atrophie musculaire observée dans plusieurs situations patho-physiologiques.

Les dosages des suppléments stimulants sont peu fiables

13/10/2016 | Etudes Compléments alimentaires et Etudes Perte de poids

 

Variability of Stimulant Levels in Nine Sports Supplements Over a 9-Month Period
International Journal of Sport Nutrition and Exercise Metabolism   Volume 26 Issue 5, October 2016       Selasi Attipoe

Many studies have found that some dietary supplement product labels do not accurately reflect the actual ingredients. However, studies have not been performed to determine if ingredients in the same dietary supplement product vary over time. The objective of this study was to assess the consistency of stimulant ingredients in popular sports supplements sold in the United States over a 9-month period. Three samples of nine popular sports supplements were purchased over the 9-month period.

The 27 samples were analyzed for caffeine and several other stimulants (including adulterants). The identity and quantity of stimulants were compared with stimulants listed on the label and stimulants found at earlier time points to determine the variability in individual products over the 9-month period. The primary outcome measure was the variability of stimulant amounts in the products examined.

Many supplements did not contain the same number and quantity of stimulants at all time points over the 9-month period. Caffeine content varied widely in five of the six caffeinated supplements compared with the initial measurement (–7% to +266%).

In addition, the stimulants—synephrine, octopamine, cathine, ephedrine, pseudoephedrine, strychnine, and methylephedrine—occurred in variable amounts in eight of the nine products. The significance of these findings is uncertain: the sample size was insufficient to support statistical analysis. In our sample of nine popular sports supplements, the presence and quantity of stimulants varied over a 9-month period. However, future studies are warranted to determine if the variability found is significant and generalizable to other supplements.

De nouvelles cellules souches découvertes dans les muscles

30/09/2016 | Echauffement et blessures et Etudes Musculation

 

The first characterization of a novel (non-satellite cell) stem cell population in human skeletal muscle
J.P. Nederveen     Appl. Physiol. Nutr. Metab. Vol. 41, 2016 S376

Skeletal muscle stem cells (satellite cells; SC) represent the primary
cell population responsible for muscle regeneration/repair. SC content
and activation has been show to increase in response to muscle
damaging exercise. However, non-satellite cell progenitors, under experimental
conditions in animals, have been identified to form skeletal
muscle
when the SC population is compromised. PW1+ interstitial
cells (PIC) have also been shown, experimentally, to contribute to
muscle repair in animals. This cell population, however, has never
been identified in humans. We sought to examine the changes in both
PIC and SC content following a single bout of eccentric exercise. Ten
sedentary males (24±3 years of age; mean±SEM) were recruited. Percutaneous
muscle biopsies from the vastus lateralis muscle were taken
prior to a bout of eccentric exercise (Pre), and 6h, 24h, and 72 h
post-exercise. Muscle fiber size, SC and PIC content were determined
via immunofluorescent microscopy. mRNA expression was assessed
by RT-PCR. The number of SC increased from Pre (10.3±0.8 Pax7+cells/
100 fibers) to 72h post-exercise (12.3±2.0 Pax7+cells/100 fibers, p<0.05).
Similarly, PW1+ cells increased from Pre (2.1±0.6 PW1+ cells/100 fibers)
to 72h post-exercise (6.8±2.5 PW1+ cells/100 fibers, p<0.05). PW1 mRNA
expression was significantly (p<0.05) increased 1.9-fold from Pre to
72h post-exercise. Here, for the first time in humans, we identify a
population of cells which are located in the interstitium that respond
to eccentrically-induced muscle damage in a similar fashion to SC.

 

Actions anti-cancers du curcuma

29/09/2016 | Etudes Compléments alimentaires et Etudes Anti-âge

 

Curcumin as a MicroRNA Regulator in Cancer: A Review
Amir Abbas Momtazi             Reviews of Physiology, Biochemistry and Pharmacology, Vol. 171 Date: 23 July 2016

Curcumin is a natural dietary polyphenol for which anti-tumor effects have been documented. Anti-inflammatory and antioxidant properties of curcumin, along with its immunomodulatory, proapoptotic, and antiangiogenic properties, are often referred to as the main mechanisms underlying the anti-tumor effects. At the molecular level, inhibition of NF-kB, Akt/PI3K, and MAPK pathways and enhancement of p53 are among the most important anticancer alterations induced by curcumin. Recent evidence has suggested that epigenetic alterations are also involved in the anti-tumor properties of curcumin. Among these curcumin-induced epigenetic alterations is modulation of the expression of several oncogenic and tumor suppressor microRNAs (miRNAs). Suppression of oncomiRs such as miR-21, miR-17-5p, miR-20a, and miR-27a and over-expression of miR-34 a/c and epithelial-mesenchymal transition-suppressor miRNAs are among the most important effects of curcumin on miRNA homeostasis. The present review will summarize the findings of in vitro and experimental studies on the impact of curcumin and its analogues on the expression of miRNAs involved in different stages of tumor initiation, growth, metastasis, and chemo-resistance.

Comment la santé des reins affecte la masse musculaire?

28/09/2016 | Echauffement et blessures et Etudes Anti-âge

 

Low glomerular filtration rate as an associated risk factor for sarcopenic muscle strength: is creatinine or cystatin C-based estimation more relevant?
Asli Tufan       The Aging Male     Pages 1-5 | Received 04 Jul 2016,  Published online: 20 Sep 2016

Introduction: We aimed to evaluate the association of a decreased glomerular-filtration-rate (GFR <60 ml/min/1.73 m2), estimated using Modification of Diet in Renal Disease (MDRD), creatinine- and cystatin C-based (CKDEPI-CR and CKDEPI-CC) Chronic Kidney Disease Epidemiology Collaboration equations with handgrip strength (HGS).

Methods: Community-dwelling males aged ≥60 years admitted to outpatient clinic were included. We used MDRD, CKDEPI-CR, and CKDEPI-CC formulas for GFR estimation and corrected these for body surface area. Muscle strength was assessed by HGS.

Results: 209 men (mean age 67.8 ± 6.4) were enrolled. Sixty-two patients (29.7%) had sarcopenic HGS. Subjects with sarcopenic HGS were older, had higher rate of a GFR < 60 ml/min/1.73 m2, had lower mid-upper arm circumference; tended to have lower creatine kinase, albumin, CKDEPI-CC-GFR levels; and higher BUN/creatinine ratio and cystatin C. Multivariate logistic regression analysis revealed a CKDEPI-CC lower than 60 ml/min/1.73 m2 as the only independent factor underlying sarcopenic HGS. Higher age tended to have an independent association. Only higher age was independently associated with low HGS when other estimations were used (p = 0.013 and p = 0.021 when MDRD and CKDEPI-CR were used, respectively).

Conclusions: There is a strong association of a GFR level of <60 ml/min/1.73 m2 with sarcopenic HGS, when CKDEPI-CC formula is used.

L’ibuprofène contre la fatigue?

28/09/2016 | Etudes cardio et Etudes sur les hormones et Echauffement et blessures

 

Ibuprofen intake increases exercise time to exhaustion: A possible role for preventing exercise-induced fatigue
F. D. Lima     Scandinavian Journal of Medicine & Science in Sports   volume 26, Issue 10 October 2016
Pages 1160–1170

Although the intake of nonsteroidal anti-inflammatory drugs (NSAIDs) intake by athletes prevents soreness, little is known concerning their role in exercise performance. This study assessed the effects of ibuprofen intake on an exhaustive protocol test after 6 weeks of swimming training in rats. Animals were divided into sedentary and training groups. After training, animals were subdivided into two subsets: saline or ibuprofen. Afterwards, three repeated swimming bouts were performed by the groups. Ibuprofen (15 mg/kg) was administered once a day. Pain measurements were performed and inflammatory and oxidative stress parameters were assayed in cerebral cortex and gastrocnemius muscle. Training, ibuprofen administration, or both combined (P 

< 0.05; 211 ± 18s, 200 ± 31s, and 279 ± 23s) increased exercise time to exhaustion.

Training decreased the acetylcholinesterase (AChE) activity (P 

< 0.05; 149 ± 11) in cerebral cortex.

Ibuprofen intake decreased the AChE activity after exhaustive protocol test in trained and sedentary rats (P < 0.05; 270 ± 60; 171 ± 38; and 273 ± 29). It also prevented neuronal tumor necrosis factor-α (TNF-α) and interleukin (IL 1β) increase. Fatigue elicited by this exhaustive protocol may involve disturbances of the central nervous system. Additive anti-inflammatory effects of exercise and ibuprofen intake support the hypothesis that this combination may constitute a more effective approach. In addition, ergogenic aids may be a useful means to prevent exercise-induced fatigue.

Page 3 sur 188 pages  <  1 2 3 4 5 >  Last »