Etudes Compléments alimentaires

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.

Effet anabolique du blanc d’œuf VS œuf entier?

25/04/2017 | Etudes Compléments alimentaires

 

Greater Stimulation of Postexercise Muscle Protein Synthesis after Consumption of Whole Eggs versus Egg Whites in Healthy Young Men
Stephan van Vliet

The majority of protein consumed in the diet is obtained from whole food sources that contain a mixture of macro- and micronutrients. Whereas the majority of research investigated the effect of isolated protein sources on protein metabolism, our aim was to assess the muscle anabolic potential of consuming a complete protein within its naturally occurring, nutrient dense food matrix during recovery from resistance exercise in young men.

In crossover trials, 10 healthy resistance-trained men (21±1 y; 88±3 kg; bodyfat: 16±1%) received primed continuous L-[ring-2H5]phenylalanine and L-[1-13C]leucine infusions. Repeated blood and muscle biopsies were collected before and after a single bout of resistance exercise (4 sets of 10 repetitions at 80% of 10-RM for both leg press and leg extensions). Immediately after resistance exercise, participants ingested intrinsically L-[5,5,5-2H3]leucine labeled whole eggs (18 g protein, 17 g fat) or egg whites (18 g protein, 0 g fat) cooked in scrambled form.

Exogenous leucine appearance rates increased (P

<0.001) after protein ingestion with peak values of 513±57 nmol leucine·kg−1·min−1 occurring at 75 min after egg white ingestion compared with 496±38 nmol leucine·kg−1·min−1 at 120 min after whole egg ingestion.

The total amount of protein derived leucine that became available in circulation over the 300 min postprandial period was similar (P=0.53) between whole egg (75±2.3%) and egg white ingestion (77±1.7%).

Whole egg ingestion supported greater post-exercise myofibrillar protein synthesis rates when compared to egg white ingestion (0.034%/h and 0.024%/h respectively; P=0.02).

We conclude that whole egg ingestion stimulates the muscle protein synthetic response more effectively than the consumption of isonitrogenous amounts of egg whites during recovery from resistance exercise in healthy young men. This effect is not attributed to divergent postprandial protein-derived amino acid availability, suggesting that some intrinsic factor within whole eggs and/or the divergent macronutrient profile may have modified the anabolic potential of this complete protein.

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 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.

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.

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