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12 février 2012 7 12 /02 /février /2012 18:09
Endocrinology. 2009 Jan;150(1):220-31. Epub 2008 Sep 4.

Hypoxia and leucine deprivation induce human insulin-like growth factor binding protein-1 hyperphosphorylation and increase its biological activity.

Source

Department of Pediatrics, University of Western Ontario, VRL Room A5-136 (WC), 800 Commissioners Road East, London, Ontario, Canada N6C 2V5.

Abstract

Fetal growth restriction is often caused by uteroplacental insufficiency that leads to fetal hypoxia and nutrient deprivation. Elevated IGF binding protein (IGFBP)-1 expression associated with fetal growth restriction has been documented. In this study we tested the hypothesis that hypoxia and nutrient deprivation induce IGFBP-1 phosphorylation and increase its biological potency in inhibiting IGF actions. HepG2 cells were subjected to hypoxia and leucine deprivation to mimic the deprivation of metabolic substrates. The total IGFBP-1 levels measured by ELISA were approximately 2- to 2.5-fold higher in hypoxia and leucine deprivation-treated cells compared with the controls. Two-dimensional immunoblotting showed that whereas the nonphosphorylated isoform is the predominant IGFBP-1 in the controls, the highly phosphorylated isoforms were dominant in hypoxia and leucine deprivation-treated cells. Liquid chromatography-tandem mass spectrometry analysis revealed four serine phosphorylation sites: three known sites (pSer 101, pSer 119, and pSer 169); and a novel site (pSer 98). Liquid chromatography-mass spectrometry was used to estimate the changes of phosphorylation upon treatment. Biacore analysis indicated that the highly phosphorylated IGFBP-1 isoforms found in hypoxia and leucine deprivation-treated cells had greater affinity for IGF-I [dissociation constant 5.83E (times 10 to the power)--0 m and 6.40E-09 m] relative to the IGFBP-1 from the controls (dissociation constant approximately 1.54E-07 m). Furthermore, the highly phosphorylated IGFBP-1 had a stronger effect in inhibiting IGF-I-stimulated cell proliferation. These findings suggest that IGFBP-1 phosphorylation may be a novel mechanism of fetal adaptive response to hypoxia and nutrient restriction.

 

Source : http://www.ncbi.nlm.nih.gov/pubmed/18772238

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12 février 2012 7 12 /02 /février /2012 15:45
J Strength Cond Res. 2010 Apr;24(4):1125-30.

Amino acid supplements and recovery from high-intensity resistance training.

Source

Department of Health and Human Performance, College of Charleston, Charleston, South Carolina, USA.

Abstract

The purpose of this study was to investigate whether short-term amino acid supplementation could maintain a short-term net anabolic hormonal profile and decrease muscle cell damage during a period of high-intensity resistance training (overreaching), thereby enhancing recovery and decreasing the risk of injury and illness. Eight previously resistance trained males were randomly assigned to either a high branched chain amino acids (BCAA) or placebo group. Subjects consumed the supplement for 3 weeks before commencing a fourth week of supplementation with concomitant high-intensity total-body resistance training (overreaching) (3 x 6-8 repetitions maximum, 8 exercises). Blood was drawn prior to and after supplementation, then again after 2 and 4 days of training. Serum was analyzed for testosterone, cortisol, and creatine kinase. Serum testosterone levels were significantly higher (p < 0.001), and cortisol and creatine kinase levels were significantly lower (p < 0.001, and p = 0.004, respectively) in the BCAA group during and following resistance training. These findings suggest that short-term amino acid supplementation, which is high in BCAA, may produce a net anabolic hormonal profile while attenuating training-induced increases in muscle tissue damage. Athletes' nutrient intake, which periodically increases amino acid intake to reflect the increased need for recovery during periods of overreaching, may increase subsequent competitive performance while decreasing the risk of injury or illness.

 

Source : http://www.ncbi.nlm.nih.gov/pubmed/20300014

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12 février 2012 7 12 /02 /février /2012 15:43

 

J Nutr. 2011 Feb;141(2):249-54. Epub 2010 Dec 15.

Higher branched-chain amino acid intake is associated with a lower prevalence of being overweight or obese in middle-aged East Asian and Western adults.

Source

Department of Nutrition, Gillings School of Global Public Health and School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.

Abstract

Beneficial effects on body weight of supplementation with BCAA, including leucine, isoleucine, and valine, have been observed in animal and human studies. However, population-based studies on dietary BCAA intake and body weight are lacking. The objective of this study was to examine the association between dietary BCAA intake and risk of overweight status/obesity among multi-ethnic populations. The International Study of Macro-/Micronutrients and Blood Pressure is a cross-sectional epidemiological investigation in China, Japan, the UK, and the US. The study cohort included 4429 men and women ages 40-59 y who were free of diabetes. Diet was assessed by 4 multi-pass 24-h recalls; data on nutrients including BCAA were derived from country-specific food tables. Overweight status and obesity were defined as BMI ≥ 25 and BMI ≥ 30 kg/m(2), respectively. Multivariable-adjusted OR of overweight status/obesity and 95% CI by quartiles of BCAA intake were estimated by logistic regression. Mean BCAA intake was 2.6 ± 0.6% energy; intake was significantly lower among Chinese participants and similar among participants from the other 3 countries. Compared with those in the first quartile, the multivariable-adjusted OR (95% CI) of overweight status from the 2nd to 4th quartiles of BCAA intake were 0.97 (0.80-1.17), 0.91 (0.75-1.11), and 0.70 (0.57-0.86), respectively (P-trend < 0.01). BCAA intake and obesity were also inversely associated (P-trend = 0.03). In conclusion, higher dietary BCAA intake is associated with lower prevalence of overweight status/obesity among apparently healthy middle-aged adults from East Asian and Western countries.

 

Source : http://www.ncbi.nlm.nih.gov/pubmed/21169225

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12 février 2012 7 12 /02 /février /2012 15:42
J Strength Cond Res. 2011 Feb;25(2):539-44.

Branched-chain amino acid supplementation lowers perceived exertion but does not affect performance in untrained males.

Source

Department of Physical Therapy and Human Movement Sciences, Sacred Heart University, Fairfield, CT, USA. greerb@sacredheart.edu

Abstract

The purpose of this study was to determine whether branched-chain amino acid (BCAA) supplementation affects aerobic performance, ratings of perceived exertion (RPE), or substrate utilization as compared with an isocaloric, carbohydrate (CHO) beverage or a noncaloric placebo (PLAC) beverage. Nine untrained males performed three 90-minute cycling bouts at 55% VO₂ peak followed by 15-minute time trials. Subjects, who were blinded to beverage selection, ingested a total of 200 kcal via the CHO or BCAA beverage before and at 60 minutes of exercise or the PLAC beverage on the same time course. RPE and metabolic measurements were taken every 15 minutes during steady-state exercise, and each of the trials was separated by 8 weeks. Plasma glucose and BCAA concentrations were measured pre- and post-exercise. A greater distance (4.6 ± 0.6 km) was traveled in the time-trial during the CHO trial than the PLAC trial (3.9 ± 0.4 km) (p < 0.05). There was no difference between the BCAA (4.4 ± 0.5 km) and PLAC trials. RPE was reduced at the 75-minute and 90-minute mark during the BCAA trial as compared with the PLAC trial. There were no significant differences found for the trial vs. time interaction in regard to respiratory exchange ratio. Thus, CHO supplementation improves performance in a loaded time-trial as compared with a PLAC beverage. BCAA supplementation, although effective at increasing blood concentrations of BCAA, did not influence aerobic performance but did attenuate RPE as compared with a PLAC beverage.

 

Source : http://www.ncbi.nlm.nih.gov/pubmed/20386134

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11 février 2012 6 11 /02 /février /2012 13:05
J Sports Sci. 2012 Feb;30(3):295-304. Epub 2011 Dec 15.

The effects of acute alcohol consumption on recovery from a simulated rugby match.

Source

a School of Sport and Exercise , Massey University , Palmerston North , New Zealand.

Abstract

Abstract In this study, we investigated the effects of acute post-exercise alcohol consumption on measures of physical performance, creatine kinase, and immunoendocrine function in the 48 h following a rugby game simulation. Ten male senior rugby union players completed a rugby game simulation after which they consumed either 1 g of alcohol per kilogram of body mass or a non-alcoholic control beverage. Agility, 15 m sprint, countermovement jump, and srummaging performance were assessed pre-simulation and 24 and 48 h post-simulation. White blood cell count, testosterone, cortisol, and creatine kinase were measured before the simulation and 30 min, 12, 24, 36, and 48 h after the simulation. One week after the first trial, participants completed the second simulation after which the other beverage was consumed. The acute consumption of alcohol after a rugby game simulation negatively affected countermovement jump performance in the days following the simulation (P = 0.028). No differences between treatments were observed for the other criterion measures made in this study. In conclusion, after 80 min of a simulated rugby game, the consumption of 1 g of alcohol per kg body mass negatively impacts lower body vertical power output. However, performance of tasks requiring repeated maximal muscular effort is not affected.

 

Source : http://www.ncbi.nlm.nih.gov/pubmed/22168345

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31 janvier 2012 2 31 /01 /janvier /2012 19:27
Int J Sport Nutr Exerc Metab. 2000 Mar;10(1):28-38.

Do regular high protein diets have potential health risks on kidney function in athletes?

Source

Department of Physiological Chemistry, Institute of Physical Education and Kinesiotherapy, Free University of Brussels, Belgium.

Abstract

Excess protein and amino acid intake have been recognized as hazardous potential implications for kidney function, leading to progressive impairment of this organ. It has been suggested in the literature, without clear evidence, that high protein intake by athletes has no harmful consequences on renal function. This study investigated body-builders (BB) and other well-trained athletes (OA) with high and medium protein intake, respectively, in order to shed light on this issue. The athletes underwent a 7-day nutrition record analysis as well as blood sample and urine collection to determine the potential renal consequences of a high protein intake. The data revealed that despite higher plasma concentration of uric acid and calcium, Group BB had renal clearances of creatinine, urea, and albumin that were within the normal range. The nitrogen balance for both groups became positive when daily protein intake exceeded 1.26 g.kg but there were no correlations between protein intake and creatinine clearance, albumin excretion rate, and calcium excretion rate. To conclude, it appears that protein intake under 2. 8 g.kg does not impair renal function in well-trained athletes as indicated by the measures of renal function used in this study.

 

Source : http://www.ncbi.nlm.nih.gov/pubmed/10722779

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13 janvier 2012 5 13 /01 /janvier /2012 08:42

Au-delà du résultat de l'étude suivante, il apparaît prépondérant de retenir que le type d'effort réalisé par les sujets, en l'occurrence des joueurs de football, est affilié à une haute intensité fractionnée. C'est justement cette même forme que l'on retrouve en musculation. Dès lors, les présents résultats pourront faire l'objet d'une application directe dans ladite discipline.

Influence of carbohydrate supplementation on skill performance during a soccer match simulation

Abstract 

Objectives

This study investigated the influence of carbohydrate supplementation on skill performance throughout exercise that replicates soccer match-play.

Design

Experimentation was conducted in a randomised, double-blind and cross-over study design.

Methods

After familiarization, 15 professional academy soccer players completed a soccer match simulation incorporating passing, dribbling and shooting on two separate occasions. Participants received a 6% carbohydrate–electrolyte solution (CHO) or electrolyte solution (PL). Precision, success rate, ball speed and an overall index (speed-precision-success; SPS) were determined for all skills. Blood samples were taken at rest, immediately before exercise, every 15min during exercise (first half: 15, 30 and 45min; second half: 60, 75 and 90min), and 10min into the half time (half-time).

Results

Carbohydrate supplementation influenced shooting (time×treatment interaction: p<0.05), where CHO attenuated the decline in shot speed and SPS index. Supplementation did not affect passing or dribbling. Blood glucose responses to exercise were influenced by supplementation (time×treatment interaction: p<0.05), where concentrations were higher at 45min and during half-time in CHO compared with PL. Blood glucose concentrations reduced by 30±1% between half-time and 60min in CHO.

Conclusions

Carbohydrate supplementation attenuated decrements in shooting performance during simulated soccer match-play; however, further research is warranted to optimise carbohydrate supplementation regimes for high-intensity intermittent sports.

 

 

Source : http://www.jsams.org/article/S1440-2440%2811%2900480-4/abstract

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11 janvier 2012 3 11 /01 /janvier /2012 19:31

Risque très élevé d'atteintes hépatiques et rénales graves avec la surconsommation de paracétamol.

 

La prise répétée de paracétamol, à des doses un peu trop élevées peut tuer, selon les résultats d’une grande étude publiée en ligne dans le British Journal of Clinical Pharmacology (cf infra).


L’étude a duré 16 ans et porté sur 938 patients admis dans un service de transplantation hépatique pour une atteinte sévère du foie. 450 de ces patients avaient pris plus de 4 grammes de paracétamol en une seule prise dans la semaine précédente. 161 avaient surconsommé du paractéamol, non pas en une seule dose mais en plus de deux prises surdosées, espacées d’au moins 8 heures, avec au total plus de 4 grammes de paracétamol en moyenne par jour dans les 7 jours précédents.


Par rapport aux patients ayant pris une seule overdose, ceux ayant consommé chaque jour un peu trop de paracétamol avaient plus de risque de mourir, d’être placés sous dialyse, et d’encéphalopathie hépatique. Près de 60 % de ces patients prenaient des doses élevées de paracétamol contre la douleur.


Le conseil de LaNutrition.fr La toxicité hépatique et rénale du paracétamol est bien connue et cette grande étude incite à la prudence. L'utilisation prolongée, à dose élevée, de paracétamol ou d'anti-inflammatoires non stéroïdiens, à l'exception de l'aspirine, augmente le risque d'insuffisance rénale. Si vous êtes amené à consommer des doses élevées de paracétamol, nous vous conseillons de les accompagner de N-acétyl-cystéine, l’antidote à la toxicité du paracétamol, qui entre dans la composition des fluidifiants bronchiques (en pharmacie). On peut également utiliser l'acide aminé méthionine.

 

Source : http://www.lanutrition.fr/les-news/un-peu-trop-de-paracetamol-un-peu-trop-souvent-peut-vous-tuer.html

 

Voici l'étude en question :

 

AIMS
Paracetamol (acetaminophen) poisoning remains the major cause of
severe acute hepatotoxicity in the UK. In this large single centre cohort
study we examined the clinical impact of staggered overdoses and
delayed presentation following paracetamol overdose.


RESULTS
Between 1992 and 2008, 663 patients were admitted with
paracetamol-induced severe liver injury, of whom 161 (24.3%) had
taken a staggered overdose. Staggered overdose patients were
significantly older and more likely to abuse alcohol than single time
point overdose patients. Relief of pain (58.2%) was the commonest
rationale for repeated supratherapeutic ingestion. Despite lower total
ingested paracetamol doses and lower admission serum alanine
aminotransferase concentrations, staggered overdose patients were
more likely to be encephalopathic on admission, require renal
replacement therapy or mechanical ventilation and had higher
mortality rates compared with single time point overdoses (37.3% vs.
27.8%, P = 0.025), although this overdose pattern did not
independently predict death. The King’s College poor prognostic
criteria had reduced sensitivity (77.6, 95% CI 70.8, 81.5) for this pattern
of overdose. Of the 396/450 (88.0%) single time point overdoses in
whom accurate timings could be obtained, 178 (44.9%) presented to
medical services >24 h following overdose. Delayed presentation
beyond 24 h post overdose was independently associated with
death/liver transplantation (OR 2.25, 95% CI 1.23, 4.12, P = 0.009).


CONCLUSIONS
Both delayed presentation and staggered overdose pattern are
associated with adverse outcomes following paracetamol overdose.
These patients are at increased risk of developing multi-organ failure
and should be considered for early transfer to specialist liver centres.

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10 janvier 2012 2 10 /01 /janvier /2012 09:01

Il est fréquent de d'entendre ou de lire que la whey est anabolique, alors que la caséine est anti-catabolique. Illustration dans cette étude (cf infra).

 

Proc Natl Acad Sci U S A. 1997 Dec 23;94(26):14930-5.

Slow and fast dietary proteins differently modulate postprandial protein accretion.

Source

Laboratoire de Nutrition Humaine, Université Clermont Auvergne, Centre de Recherche en Nutrition Humaine, BP 321, 63009 Clermont-Ferrand Cedex 1, France.

Abstract

The speed of absorption of dietary amino acids by the gut varies according to the type of ingested dietary protein. This could affect postprandial protein synthesis, breakdown, and deposition. To test this hypothesis, two intrinsically 13C-leucine-labeled milk proteins, casein (CAS) and whey protein (WP), of different physicochemical properties were ingested as one single meal by healthy adults. Postprandial whole body leucine kinetics were assessed by using a dual tracer methodology. WP induced a dramatic but short increase of plasma amino acids. CAS induced a prolonged plateau of moderate hyperaminoacidemia, probably because of a slow gastric emptying. Whole body protein breakdown was inhibited by 34% after CAS ingestion but not after WP ingestion. Postprandial protein synthesis was stimulated by 68% with the WP meal and to a lesser extent (+31%) with the CAS meal. Postprandial whole body leucine oxidation over 7 h was lower with CAS (272 +/- 91 micromol.kg-1) than with WP (373 +/- 56 micromol.kg-1). Leucine intake was identical in both meals (380 micromol.kg-1). Therefore, net leucine balance over the 7 h after the meal was more positive with CAS than with WP (P < 0.05, WP vs. CAS). In conclusion, the speed of protein digestion and amino acid absorption from the gut has a major effect on whole body protein anabolism after one single meal. By analogy with carbohydrate metabolism, slow and fast proteins modulate the postprandial metabolic response, a concept to be applied to wasting situations.

 

Source : http://www.ncbi.nlm.nih.gov/pubmed/9405716

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10 janvier 2012 2 10 /01 /janvier /2012 08:52
Am J Clin Nutr. 2007 Apr;85(4):981-8.

A controlled trial of reduced meal frequency without caloric restriction in healthy, normal-weight, middle-aged adults.

Source

Beltsville Human Nutrition Research Center, US Department of Agriculture, Agriculture Research Service, Beltsville, MD, USA.

Abstract

BACKGROUND:

Although consumption of 3 meals/d is the most common pattern of eating in industrialized countries, a scientific rationale for this meal frequency with respect to optimal health is lacking. A diet with less meal frequency can improve the health and extend the lifespan of laboratory animals, but its effect on humans has never been tested.

OBJECTIVE:

A pilot study was conducted to establish the effects of a reduced-meal-frequency diet on health indicators in healthy, normal-weight adults.

DESIGN:

The study was a randomized crossover design with two 8-wk treatment periods. During the treatment periods, subjects consumed all of the calories needed for weight maintenance in either 3 meals/d or 1 meal/d.

RESULTS:

Subjects who completed the study maintained their body weight within 2 kg of their initial weight throughout the 6-mo period. There were no significant effects of meal frequency on heart rate, body temperature, or most of the blood variables measured. However, when consuming 1 meal/d, subjects had a significant increase in hunger; a significant modification of body composition, including reductions in fat mass; significant increases in blood pressure and in total, LDL-, and HDL-cholesterol concentrations; and a significant decrease in concentrations of cortisol.

CONCLUSIONS:

Normal-weight subjects are able to comply with a 1 meal/d diet. When meal frequency is decreased without a reduction in overall calorie intake, modest changes occur in body composition, some cardiovascular disease risk factors, and hematologic variables. Diurnal variations may affect outcomes.

 

Source : http://www.ncbi.nlm.nih.gov/pubmed/17413096

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  • : Gasser Yves &amp; Fonta Frédéric
  • Gasser Yves &amp; Fonta Frédéric
  • : Vous pourrez retrouver sur ce blog l'ensemble des articles rédigés par Gasser Yves, préparateur sportif à Perpignan, Champion de France, d'Europe et 3ème Monde Masters WPF 1997/1998, en étroite collaboration avec Fonta Frédéric, ainsi que diverses données relatives à l'entrainement ou la diététique. Bonne lecture à tous!
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