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Le Viagra est-il aussi un anti-aromatase?

01/12/2016 | Etudes Perte de poids et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

Effect of sildenafil on human aromatase activity: From in vitro structural analysis to catalysis and inhibition in cells
The Journal of Steroid Biochemistry and Molecular Biology Volume 165, Part B, January 2017, Pages 438–447       Roberta Baravalle

Highlights
• Human aromatase binds the drug sildenafil showing a Type II spectrum.
• EPR spectroscopy shows that sildenafil does not directly bind heme iron.
• Sildenafil acts as a mixed and partial inhibitor on human aromatase.
• Aromatase inhibition by sildenafil is confirmed in ST14A and MCF-7 cells.

Aromatase catalyses the conversion of androgens into estrogens and is a well-known target for breast cancer therapy. As it has been suggested that its activity is affected by inhibitors of phosphodiesterase-5, this work investigates the potential interaction of sildenafil with aromatase. This is carried out both at molecular level through structural and kinetics assays applied to the purified enzyme, and at cellular level using neuronal and breast cancer cell lines.

Sildenafil is found to bind to aromatase with a KD of 0.58 ± 0.05 μM acting as a partial and mixed inhibitor with a maximal inhibition of 35 ± 2%. Hyperfine sublevel correlation spectroscopy and docking studies show that sildenafil binds to the heme iron via its 6th axial water ligand.

These results also provide information on the starting molecular scaffold for the development of new generations of drugs designed to inhibit aromatase as well as phosphodiesterase-5, a new emerging target for breast cancer therapy.

Le curcuma est-il un inhibiteur de la 5 alpha réductase?

27/11/2016 | Etudes Compléments alimentaires et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

A new label-free screen for steroid 5α-reductase inhibitors using LC-MS
Steroids Volume 116, December 2016, Pages 67–75       Jukkarin Srivilai

Highlights
• A novel assay for 5 alpha reductase (S5αR) activity determination based on LC-MS quantitation of DHT.
• The assay showed high reproducibility and selectivity with Z′ factor of 0.77.
• The method was successfully used to quantify S5αR inhibitory activity of some herbal extracts.

Steroid 5α-reductase (S5αR) plays an important role in metabolizing testosterone into active androgen dihydrotestosterone (DHT) which is involved in many androgen dependent disorders, such as androgenic alopecia, benign prostatic hyperplasia and acne. The method for screening for S5αR inhibition is key in finding new antagonists. In this study, the label-free S5αR inhibitory assay using LC-MS was developed. S5αR type 1 enzyme was obtained from LNCaP prostate cancer cells. The enzymatic assay was optimised for enzyme-substrate (testosterone) concentration, NADPH-cofactor concentration, solvent tolerance, enzyme activity stability and incubation time. The developed assay was validated by measuring the signal to background ratio (S/B), the signal to noise ratio (S/N), the signal window (SW) and the zeta factor Z′ in accordance with published bioassay guidelines. The enzymatic reaction was performed in 96-well plates and DHT formation was determined by LC-MS. S/B, S/N, SW and Z′ factor were well above acceptable criteria and the reproducibility was good using Z′ factor other 3 days and further validated by dutasteride and finasteride inhibition. The method was successfully applied to quantify S5αR inhibitory activity of some Thai herbal extracts.

Two plant extracts, Impatiens balsamina L. and Curcuma longa L. showed IC50 at 5.4 ± 0.2 and 9.0 ± 1.2 μg mL−1 and are therefore promising sources of new S5αR inhibitors. The assay has high selectability and reproducibility and suited to medium throughput screening required by phytochemistry.

Quels impacts des corps cétoniques chez le sportif?

18/11/2016 | Etudes Compléments alimentaires et Etudes Perte de poids

 

Metabolism of ketone bodies during exercise and training: physiological basis for exogenous supplementation
Mark Evans                   J Physiol 2016

Optimising training and performance through nutrition strategies is central to supporting elite sportspeople, much of which has focussed on manipulating the relative intake of carbohydrate and fat and their contributions as fuels for energy provision. The ketone bodies, namely acetoacetate, acetone, and β-hydroxybutyrate (βHB), are produced in the liver during conditions of reduced carbohydrate availability and serve as an alternative fuel source for peripheral tissues including brain, heart and skeletal muscle.

Ketone bodies are oxidised as a fuel source during exercise, are markedly elevated during the post-exercise recovery period, and the ability to utilise ketone bodies is higher in exercise-trained skeletal muscle. The metabolic actions of ketone bodies can alter fuel selection through attenuating glucose utilisation in peripheral tissues, anti-lipolytic effects on adipose tissue, and attenuation of proteolysis in skeletal muscle. Moreover, ketone bodies can act as signalling metabolites with βHB acting as an inhibitor of histone deacetylases, an important regulator of the adaptive response to exercise in skeletal muscle.

Recent development of ketone esters facilitates acute ingestion of βHB that results in nutritional ketosis without necessitating restrictive dietary practices. Initial reports suggest this strategy alters the metabolic response to exercise and improves exercise performance, while other lines of evidence suggest roles in recovery from exercise.

The present review focuses on the physiology of ketone bodies during and after exercise and in response to training, with specific interest in exploring the physiological basis for exogenous ketone supplementation and potential benefits for performance and recovery in athletes.

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.

 

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