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Rôles de la périlipine dans lipolyse musculaire

04/07/2015 | Etudes cardio et Etudes Perte de poids

 

Piecing together the puzzle of perilipin proteins and skeletal muscle lipolysis
Rebecca E.K. MacPherson   Physiologie appliquée, nutrition et métabolisme, 2015, 40(7): 641-651

La régulation de la lipolyse et de l’oxydation des gras dans le muscle squelettique est un processus complexe impliquant de nombreuses protéines et enzymes. D’après des travaux récents, les protéines PLIN du muscle squelettique joueraient vraisemblablement un rôle dans l’hydrolyse des triglycérides stockés dans les gouttelettes de lipides et dans le passage des acides gras pour leur oxydation dans la mitochondrie. Dans les adipocytes, PLIN1 régule la lipolyse en interagissant avec le gène d’identification comparative-58 (CGI-58), un activateur de la lipase des triglycérides du tissu adipeux (ATGL). Lors de la stimulation de la lipolyse, PLIN1 est phosphorylée et CGI-58 est libéré pour activer ATGL et amorcer la dégradation des triglycérides. En l’absence de PLIN1 dans le muscle squelettique, il semble que d’autres membres de la famille des PLIN joueraient ce rôle.

Cette analyse documentaire porte principalement sur l’expression des protéines PLIN dans le muscle squelettique: PLIN2, PLIN3 et PLIN5. Jusqu’à ce jour, la majorité des études traitant de ces protéines PLIN utilisaient des tissus autres que musculaires et des cultures cellulaires pour définir leur rôle potentiel. Les résultats des travaux utilisant ces modèles confèrent aux protéines PLIN un rôle de séquestration des lipases dans des conditions de base et de collaboration possible dans la translocation des lipases et de leur activité au cours de la lipolyse. Dans le muscle squelettique, PLIN2 tend à copier le contenu lipidique et pourrait jouer un rôle dans la croissance et la stabilité des gouttelettes de gras par l’interaction des lipases à la surface des gouttelettes de lipides. Le rôle de PLIN3 et PLIN5 dans le muscle squelettique est plus complexe qu’on ne pense, car on les observe non seulement sur les gouttelettes de lipides, mais aussi sur les mitochondries. De toute évidence, il faut réaliser d’autres études pour élucider les mécanismes complexes par lesquels les protéines PLIN contribuent au métabolisme des lipides dans le muscle squelettique.

Les femmes répondent moins bien au cardio que les hommes!

01/07/2015 | Etudes cardio et Etudes Perte de poids et Etudes Anti-âge

 

Females have a blunted cardiovascular response to one year of intensive supervised endurance training
Erin J. Howden   Journal of Applied Physiology Published 1 July 2015 Vol. 119 no.  1,  37-46

Cross-sectional studies in athletes suggest that endurance training augments cardiovascular structure and function with apparently different phenotypes in athletic males and females. It is unclear whether the longitudinal response to endurance training leads to similar cardiovascular adaptations between sexes. We sought to determine whether males and females demonstrate similar cardiovascular adaptations to 1 yr of endurance training, matched for training volume and intensity.

Twelve previously sedentary males (26 ± 7, n = 7) and females (31 ± 6, n = 5) completed 1 yr of progressive endurance training. All participants underwent a battery of tests every 3 mo to determine maximal oxygen uptake (V̇o2max) and left ventricle (LV) function and morphology (cardiac magnetic resonance imaging). Pulmonary artery catheterization was performed before and after 1 yr of training, and pressure-volume and Starling curves were constructed during decreases (lower-body negative pressure) and increases (saline infusion) in cardiac volume.

Males progressively increased V̇o2max, LV mass, and mean wall thickness, before reaching a plateau from month 9 to 12 of training. In contrast, despite exactly the same training, the response in females was markedly blunted, with V̇o2max, LV mass, and mean wall thickness plateauing after only 3 mo of training.
The response of LV end-diastolic volume was not influenced by sex (males +20% and females +18%). After training Starling curves were shifted upward and left, but the effect was greatest in males (interaction P = 0.06).

We demonstrate for the first time clear sex differences in response to 1 yr of matched endurance training, such that the development of ventricular hypertrophy and increase in V̇o2max in females is markedly blunted compared with males.

De combien la muscu élève t’elle le métabolisme?

01/07/2015 | Etudes cardio et Etudes Musculation et Etudes Perte de poids et Etudes Anti-âge

 

De quasiment rien!

Effect of resistance training on resting metabolic rate and its estimation by a dual-energy X-ray absorptiometry metabolic map
European Journal of Clinical Nutrition (2015) 69, 831–836;  J C Aristizaba

Background/objectives:

Fat-free mass (FFM) is the major predictor of resting metabolic rate (RMR). As protein supplementation during resistance training may augment gains in FFM, we investigated the effects of resistance training combined with protein supplementation on RMR and whether RMR responses could be estimated by a dual-energy X-ray absorptiometry (DXA) metabolic map.


Subjects/methods:

Healthy adults completed a whole-body periodized resistance training program consisting of 96 workouts (~9 months). Participants were randomly assigned to supplement with whey protein (whey; n=18), soy protein (soy; n=21) or carbohydrate (carb; n=22). RMR was measured using indirect calorimetry (RMRIC) and estimated by DXA metabolic mapping (RMRMM) pretraining and posttraining.


Results:

RMRIC increased from pretraining to posttraining in the whole cohort (1653±302 to 1726±291 kcal/day, P=0.001) without differences between the groups. Delta RMRIC and RMRMM (73±158 vs 52±41 kcal/day were not significantly different by t-test (P=0.303), although they were not significantly correlated (r=0.081; P=0.535). Stepwise regression identified 43% of the shared variance in delta RMRIC using total serum thyroxine, RMRIC and FFM at baseline (P=0.009).


Conclusions:

These results indicate that 9 months of resistance training significantly increased RMR ~5% on average, but there was wide variability between individuals, which can be partially accounted for by changes in FFM and thyroid hormones.

La vitamine B12 comme cause de l’acné ?

25/06/2015 | Etudes Compléments alimentaires et Etudes Perte de poids et Etudes Anti-âge

 

Etude qui montre que les causes de l’acné sont très diverses

Vitamin B12 modulates the transcriptome of the skin microbiota in acne pathogenesis
Dezhi Kang   Science Translational Medicine 24 Jun 2015: Vol. 7, Issue 293, pp. 293ra103

Various diseases have been linked to the human microbiota, but the underlying molecular mechanisms of the microbiota in disease pathogenesis are often poorly understood. Using acne as a disease model, we aimed to understand the molecular response of the skin microbiota to host metabolite signaling in disease pathogenesis. Metatranscriptomic analysis revealed that the transcriptional profiles of the skin microbiota separated acne patients from healthy individuals. The vitamin B12 biosynthesis pathway in the skin bacterium Propionibacterium acnes was significantly down-regulated in acne patients.

We hypothesized that host vitamin B12 modulates the activities of the skin microbiota and contributes to acne pathogenesis. To test this hypothesis, we analyzed the skin microbiota in healthy subjects supplemented with vitamin B12. We found that the supplementation repressed the expression of vitamin B12 biosynthesis genes in P. acnes and altered the transcriptome of the skin microbiota.

One of the 10 subjects studied developed acne 1 week after vitamin B12 supplementation.

To further understand the molecular mechanism, we revealed that vitamin B12 supplementation in P. acnes cultures promoted the production of porphyrins, which have been shown to induce inflammation in acne. Our findings suggest a new bacterial pathogenesis pathway in acne and provide one molecular explanation for the long-standing clinical observation that vitamin B12 supplementation leads to acne development in a subset of individuals. Our study discovered that vitamin B12, an essential nutrient in humans, modulates the transcriptional activities of skin bacteria, and provided evidence that metabolite-mediated interactions between the host and the skin microbiota play essential roles in disease development.

Découverte du secret de Popeye pour sécher

23/06/2015 | Etudes Compléments alimentaires et Etudes Perte de poids

 

Acute Effects of a Spinach Extract Rich in Thylakoids on Satiety: A Randomized Controlled Crossover Trial
Journal of the American College of Nutrition Published online: 01 Jun 2015   Candida J. Rebello
 
Objective: By retarding fat digestion, thylakoids, the internal photosynthetic membrane system of green plants, promote the release of satiety hormones. This study examined the effect of consuming a single dose of concentrated extract of thylakoids from spinach on satiety, food intake, lipids, and glucose compared to a placebo.

Design: Sixty overweight and obese individuals enrolled in a double-blind randomized crossover study consumed the spinach extract or placebo in random order at least a week apart. Blood was drawn for assessments of lipids and glucose before a standard breakfast meal, followed 4 hours later by a 5 g dose of the extract and a standard lunch. Visual analog scales were administered before lunch and at intervals until an ad libitum pizza dinner served 4 hours later. Two hours after lunch a second blood draw was conducted. Mixed models were used to analyze response changes.

Results: Compared to placebo, consuming the spinach extract reduced hunger (p < 0.01) and longing for food over 2 hours (p < 0.01) and increased postprandial plasma glucose concentrations (p < 0.01). There were no differences in plasma lipids and energy intake at dinner, but males showed a trend toward decreased energy intake (p = 0.08).

Conclusions: At this dose, the spinach extract containing thylakoids increases satiety over a 2-hour period compared to a placebo. Thylakoid consumption may influence gender-specific food cravings.

Supplémentation en nitrate et santé rénale?

19/06/2015 | Etudes Compléments alimentaires et Etudes Anti-âge et Etudes sur les boosters sexuels et la sexualité

 

Personne n’est mort mais 1 semaine de tests, c’est pas long!
Nitrate Supplementation, Exercise, and Kidney Function: Are There Detrimental Effects?
Medicine & Science in Sports & Exercise: July 2015 - Volume 47 - Issue 7 - p 1519–1522     CARPENTIER, ALAIN

Purpose: Recently, dietary supplementation with inorganic nitrate (NO3−) has been proposed to endurance athletes to increase their performance. However, it has been suggested that an excess of NO3− might be harmful. The present study analyzed the effect of NO3− supplementation on kidney function.

Methods: Thirteen young male subjects performed a 20-min cycling exercise at 85% of the maximal oxygen capacity. Seven days before exercise, the subjects ingested either a placebo (Pl) or 450 mg of potassium nitrate (PN) per day. Venous blood samples and urine collections were collected before and immediately after exercise and after 60 min of recovery. Glomerular filtration rates (GFR) and clearances (Cl) were calculated from serum content and urine output for creatinine (Crn), albumin (Alb), and urea.

Results: Under resting conditions, GFR and all clearance measures did not differ between Pl and PN. Immediately after exercise, GFR remained stable in both Pl and PN, whereas Cl-urea decreased significantly (P < 0.05) in Pl (−44%) and PN (−49%). Alb urine outputs were enhanced by 18- to 20-fold in Pl and PN, respectively (P < 0.05). After the recovery period, GFR remained enhanced under Pl conditions, whereas Cl-urea returned to initial values in placebo and nitrate supplementation. Alb output and Cl-Alb remained enhanced under PN conditions.

Conclusion: These results mainly indicate that dietary nitrate supplementation over a week does not induce any specific kidney function modifications either at rest or during sustained submaximal exercise as compared with Pl.

Signature génétique d’un champion de sprint

17/06/2015 | Musculation des quadriceps et Etudes Musculation

 

Skeletal muscle signature of a champion sprint runner
Scott Trappe   Journal of Applied Physiology Published 15 June 2015 Vol. 118 no.  12,  1460-1466

We had the unique opportunity to study the skeletal muscle characteristics, at the single fiber level, of a world champion sprint runner who is the current indoor world record holder in the 60-m hurdles (7.30 s) and former world record holder in 110-m hurdles (12.91 s). Muscle biopsies were obtained from the vastus lateralis at rest and 4 h after a high-intensity exercise challenge (4 × 7 repetitions of resistance exercise). Single muscle fiber analyses were conducted for fiber type distribution (myosin heavy chain, MHC), fiber size, contractile function (strength, speed, and power) and mRNA expression (before and after the exercise bout).

The world-class sprinter’s leg muscle had a high abundance (24%) of the pure MHC IIx muscle fibers with a total fast-twitch fiber population of 71%.

Power output of the MHC IIx fibers (35.1 ± 1.4 W/l) was 2-fold higher than MHC IIa fibers (17.1 ± 0.5 W/l) and 14-fold greater than MHC I fibers (2.5 ± 0.1 W/l).

Additionally, the MHC IIx fibers were highly responsive to intense exercise at the transcriptional level for genes involved with muscle growth and remodeling (Fn14 and myostatin). To our knowledge, the abundance of pure MHC IIx muscle fibers is the highest observed in an elite sprinter. Further, the power output of the MHC IIa and MHC IIx muscle fibers was greater than any human values reported to date. These data provide a myocellular basis for the high level of sprinting success achieved by this individual.

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