Etudes Compléments alimentaires

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

• 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.

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

• 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.

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