Etudes Anti-âge

L’équilibre en sodium est plus compliqué qu’il n’y parait

09/05/2017 | Etudes sur les hormones et Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Increased salt consumption induces body water conservation and decreases fluid intake
Natalia Rakova       J Clin Invest April 17, 2017 - More info

The idea that increasing salt intake increases drinking and urine volume is widely accepted. We tested the hypothesis that an increase in salt intake of 6 g/d would change fluid balance in men living under ultra-long-term controlled conditions.

METHODS. Over the course of 2 separate space flight simulation studies of 105 and 205 days’ duration, we exposed 10 healthy men to 3 salt intake levels (12, 9, or 6 g/d). All other nutrients were maintained constant. We studied the effect of salt-driven changes in mineralocorticoid and glucocorticoid urinary excretion on day-to-day osmolyte and water balance.

RESULTS. A 6-g/d increase in salt intake increased urine osmolyte excretion, but reduced free-water clearance, indicating endogenous free water accrual by urine concentration. The resulting endogenous water surplus reduced fluid intake at the 12-g/d salt intake level. Across all 3 levels of salt intake, half-weekly and weekly rhythmical mineralocorticoid release promoted free water reabsorption via the renal concentration mechanism. Mineralocorticoid-coupled increases in free water reabsorption were counterbalanced by rhythmical glucocorticoid release, with excretion of endogenous osmolyte and water surplus by relative urine dilution. A 6-g/d increase in salt intake decreased the level of rhythmical mineralocorticoid release and elevated rhythmical glucocorticoid release. The projected effect of salt-driven hormone rhythm modulation corresponded well with the measured decrease in water intake and an increase in urine volume with surplus osmolyte excretion.

CONCLUSION. Humans regulate osmolyte and water balance by rhythmical mineralocorticoid and glucocorticoid release, endogenous accrual of surplus body water, and precise surplus excretion.

Vitamine P4 contre la fatigue

30/04/2017 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Short-term effects of troxerutin (vitamin P4) on muscle fatigue and gene expression of Bcl-2 and Bax in the hepatic tissue of rats

Mohammad Zamanian         Revue canadienne de physiologie et pharmacologie 2017

Dans les présents travaux, nous avons étudié l’effet de la troxérutine (TRX) sur la fatigue musculaire et l’expression des gènes Bcl-2 et Bax dans le tissu hépatique de rat. Nous avons réparti aléatoirement 40 rats Wistar mâles dans les quatre groupes suivants : témoin et administration de TRX à 75 (TRX75), 150 (TRX150) et 300 mg/kg par jour (TRX300). Les groupes TRX et placebo ont reçu pendant 7 jours de la TRX et de l’eau, respectivement. Le 7e jour, tous les animaux ont été euthanasiés immédiatement après un test de nage menant à l’épuisement, et nous avons mesuré plusieurs paramètres biochimiques liés à la fatigue et à l’expression des gènes Bcl-2 et Bax dans le tissu hépatique. Nos résultats ont montré que dans le groupe TRX300, le temps de nage écoulé avant l’épuisement était 1,2 fois plus élevé que dans le groupe témoin (résultats statistiquement significatifs : P < 0,001).

Dans le groupe TRX300, l’activité de l’ALT diminuait et l’activité hépatique de la SOD augmentait de façons nettement plus marquées que dans le groupe témoin (P < 0,05 et P < 0,01, respectivement). De plus, la TRX entraînait une diminution de l’expression de l’ARNm du gène Bax et une augmentation du rapport Bcl-2/Bax nettement plus marquées que dans le groupe témoin (P < 0,001 dans les deux cas).

D’après nos données, la TRX exerce une action anti-apoptotique et hépatoprotectrice à la suite d’un exercice de nage menant à l’épuisement.

Rôle de la sirtuine 1 dans l’hypertrophie

02/03/2017 | Etudes sur les hormones et Etudes Musculation et Etudes Anti-âge

 

SIRT1 may play a crucial role in overload induced hypertrophy of skeletal muscle
Erika Koltai J physiol 2017

Significant skeletal muscle mass guarantees functional wellbeing and is important for high level performance in many sports. Although the molecular mechanism for skeletal muscle hypertrophy has been well-studied, it still is not completely understood. In the present study, we used a functional overload model to induce plantaris muscle hypertrophy by surgically removing the soleus, and gastrocnemius muscles in rats. Two weeks of muscle ablation resulted in a 40% increase in muscle mass, which was associated with a significant increase in SIRT1 content and activity (P

< 0.001). SIRT1-regulated Akt, eNOS, GLUT4 levels were also induced in hypertrophied muscles, and SIRT1 levels correlated with muscle mass, paired box protein 7 (Pax7), proliferating cell nuclear antigen (PCNA) and nicotinamide phosphoribosyltransferase (Nampt) levels. Alternatively, decreased FOXO1 and increased K48 polyubiquitination also suggest that SIRT1 could also be involved in the catabolic process of hypertrophy. Furthermore, increased levels of K63 and muscle RING finger 2 (MuRF2) protein could also be important enhancers of muscle mass. We report here that the levels of miR1 and miR133a decrease in hypertrophy and negatively correlate with muscle mass, SIRT1, and Nampt levels. Our results reveal a strong agreement between SIRT1 levels and activity, SIRT1 regulated pathways, and overload-induced hypertrophy.

These findings, along with the well-known regulatory

roles that SIRT1 plays in modulating both anabolic and catabolic pathways, allow us to propose the hypothesis that SIRT1 may actually play a crucial causal role in overload induced hypertrophy of skeletal muscle. This hypothesis will now require rigorous direct and functional testing.

Le mystère des aliments riche en mélatonine

31/12/2016 | Etudes sur les hormones et Etudes Compléments alimentaires et Etudes Anti-âge

 

Are the proposed benefits of melatonin-rich foods too hard to swallow?
David J. Kennaway     Critical Reviews in Food Science and Nutrition   2016 Pages 958-962

Melatonin has been proposed as a potent anti-oxidant, and its presence in many plants and foods has been suggested to be beneficial for health. Indeed, the concentrations of melatonin in blood and the melatonin metabolite 6 sulphatoxymelatonin in urine have been found to increase significantly after ingestion of melatonin-rich foods. In this review, the studies have been critically evaluated in light of the reported plant melatonin concentrations and our knowledge of pharmacokinetics of orally administered pure melatonin. In the case of studies involving measurement of plasma melatonin following ingestion of beer or fruits, the reported increase in melatonin is not consistent with the amount of melatonin ingested. Similarly, the amount of melatonin metabolite excreted following ingestion of melatonin-rich foods greatly exceeded the amount of melatonin ingested.

It is concluded that studies reporting the appearance of melatonin in blood and its metabolites in urine following ingestion of melatonin-rich foods are flawed. While there may be health benefits for certain foods, it is difficult to accept that these are due to their low melatonin content.

 

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.

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.

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