152 research outputs found
Accumulation of intramuscular toxic lipids, a link between fat mass accumulation and sarcopeniaâ
Aging is characterized by a loss in muscle mass and function, which is defined as sarcopenia. It weakens individuals by increasing the risk of falls and altering their quality of life. The loss of muscle mass results from the age-related impairment of the anabolic effect of nutrients and insulin, which normally increase and decrease muscle protein synthesis and degradation rates respectively. Alterations in muscle protein metabolism have been related to the accumulation of body fat and intramyocellular lipids. In particular, some lipid species such as ceramides or diacylglycerols have been described as inhibitors of the insulin signaling pathway in different models. Accumulation of these molecules in skeletal muscle could result from a lowered buffering capacity of circulating fatty acids by adipose tissue in response to the meal, a reduction of mitochondrial oxidative capacities or chronic inflammation. However, some nutritional strategies have been identified to limit or prevent the accumulation of lipotoxic metabolites and to improve the sensitivity of muscle to nutrients or insulin
Knee extension strength in obese and nonobese male adolescents
The aim of the present study was to compare âabsoluteâ and ârelativeâ knee extension strength between obese and nonobese adolescents. Ten nonobese and 12 severely obese adolescent boys of similar chronological age, maturity status, and height were compared. Total body and regional soft tissue composition were determined using dual-energy X-ray absorptiometry (DXA). Knee extensors maximum voluntary contraction (MVC) torque was measured using an isometric dynamometer at a knee angle of 60° (0° is full extension). Absolute MVC torque was significantly higher in obese adolescents than in controls. However, although MVC torque expressed per unit of body mass was found to be significantly lower in obese adolescent boys, no significant difference in MVC torque was found between groups when normalized to fat-free mass. Conversely, when correcting for thigh lean mass and estimated thigh muscle mass, MVC torque was significantly higher in the obese group (17.9% and 22.2%, respectively; P <0.05). To conclude, our sample of obese adolescent boys had higher absolute and relative knee extension strength than our nonobese controls. However, further studies are required to ascertain whether or not relative strength, measured with more accurate in vivo methods such as magnetic resonance imaging, is higher in obese adolescents than in nonobese controls
Impact of an obesogenic diet program on bone densitometry, micro architecture and metabolism in male rat.
International audienceABSTRACT: Background The relationships between fat mass and bone tissue are complex and not fully elucidated. A high-fat/high-sucrose diet has been shown to induce harmful effects on bone micro architecture and bone biomechanics of rat. When such diet leads to obesity, it may induce an improvement of biomechanical bone parameters in rodent. Here, we examined the impact of a high-fat/high-sucrose diet on the body composition and its resulting effects on bone density and structure in male rats. Forty three Wistar rats aged 7 months were split into 3 groups: 1 sacrificed before diet (BD, n=14); 1 subjected to 16 weeks of high-fat/high-sucrose diet (HF/HS, n=14); 1 subjected to standard diet (Control, n=15). Abdominal circumference and insulin sensitivity were measured and visceral fat mass was weighed. The bone mineral density (BMD) was analyzed at the whole body and tibia by densitometry. Microcomputed tomography and histomorphometric analysis were performed at L2 vertebrae and tibiae to study the trabecular and cortical bone structures and the bone cell activities. Osteocalcin and CTX levels were performed to assess the relative balance of the bone formation and resorption. Differences between groups have been tested with an ANOVA with subsequent Scheffe post-hoc test. An ANCOVA with global mass and global fat as covariates was used to determine the potential implication of the resulting mechanical loading on bone. RESULTS: The HF/HS group had higher body mass, fat masses and abdominal circumference and developed an impaired glucose tolerance compared to Control group (p<0.001). Whole body bone mass (p<0.001) and BMD (p<0.05) were higher in HF/HS group vs. Control group. The trabecular thickness at vertebrae and the cortical porosity of tibia were improved (p<0.05) in HF/HS group. Bone formation was predominant in HF/HS group while an unbalance bone favoring bone resorption was observed in the controls. The HF/HS and Control groups had higher total and abdominal fat masses and altered bone parameters vs. BD group. Conclusions The HF/HS diet had induced obesity and impaired glucose tolerance. These changes resulted in an improvement of quantitative, qualitative and metabolic bone parameters. The fat mass increase partly explained these observations
Quantitative and qualitative protein intakes to fight sarcopenia during aging
International audienceAging is associated with modifications of protein metabolism, in : particular at skeletal muscle level. This age-related loss of muscle mass could be counteracted by adequate nutritional intakes. Recent observations clearly showed that intake of high-digestible leucine-rich proteins, change in daily protein pattern or specific amino acid supplementation may be beneficial to improve muscle anabolic response in elderly people. However these nutritional strategies have to be tested using large epidemiological studies before being applied to the general aged population
La lutte contre la sarcopénie passe-t-elle par les protéines ?
National audienceLe vieillissement se caractĂ©rise par une perte de la masse, de la qualitĂ© et des fonctions contractiles musculaires, appelĂ©e âsarcopĂ©nieâ. Une perte de la sensibilitĂ© musculaire Ă certains facteurs anaboliques apparaĂźt au cours du vieillissement, en particulier une rĂ©sistance Ă la stimulation de la synthĂšse protĂ©ique musculaire par la prise du repas. Les protĂ©ines alimentaires sont les matĂ©riaux et les signaux anabolisants permettant la construction protĂ©ique musculaire. Une altĂ©ration de lâassimilation et de la rĂ©ponse du mĂ©tabolisme protĂ©ique musculaire aux acides aminĂ©s issus du repas a Ă©tĂ© observĂ©e chez lâindividu ĂągĂ©. Au sein de lâalimentation, en dehors des acides aminĂ©s, dâautres nutriments sont des rĂ©gulateurs positifs (vitamine D, olĂ©ate) ou nĂ©gatifs (palmitate) de lâanabolisme protĂ©ique musculaire. Ces nutriments agissent par des mĂ©canismes spĂ©cifiques et/ou de concert avec les acides aminĂ©s. Un dĂ©faut dâadaptation et/ou de rĂ©ponse des cellules musculaires Ă lâensemble de ces nutriments a Ă©tĂ© observĂ© au cours du vieillissement, participant Ă la perte protĂ©ique musculaire et donc au dĂ©veloppement de la sarcopĂ©nie du sujet Ăąg
4.12. Les compléments alimentaires
Selon le dĂ©cret n° 2006-352, « les complĂ©ments alimentaires sont des denrĂ©es alimentaires dont le but est de complĂ©ter le rĂ©gime alimentaire normal et qui constituent une source concentrĂ©e de nutriments ou dâautres substances ayant un effet nutritionnel ou physiologique ». Les complĂ©ments alimentaires font lâobjet de dĂ©clarations auprĂšs de la DGCCRF mais leur commercialisation ne nĂ©cessite pas dâautorisation individuelle de mise sur le marchĂ©. Les complĂ©ments alimentaires reprĂ©sentent une gam..
Les effets musculaires de la vitamine D : application Ă la perte musculaire liĂ©e Ă lâĂąge
Au-delà de ses rÎles biologiques classiques sur la santé osseuse, les effets
extra-squelettiques de la vitamine D font actuellement lâobjet de nombreuses recherches.
La prĂ©sence du rĂ©cepteur de la vitamine D dans la plupart des tissus de lâorganisme vient
dâailleurs renforcer lâargument en faveur de ses fonctions multiples. Parmi celles-ci,
lâeffet de la vitamine D sur la masse et les performances musculaires a Ă©tĂ© longtemps
pressenti. En effet, dans la GrĂšce Antique, HĂ©rodote recommandait le soleil comme un
remĂšde pour les « muscles faibles et mous », et les anciens Olympiens recevaient lâordre de
se coucher exposés aux rayons du soleil pour améliorer leurs performances physiques. En
1952, Spellerberg, un physiologiste du sport, a réalisé une vaste étude portant sur les
effets de lâirradiation UV sur les performances dâathlĂštes de haut niveau. Suite aux
résultats positifs de cette investigation, ce scientifique dû informer le Comité Olympique
que lâirradiation UV prĂ©sentait un effet « convaincant » sur la performance physique et les
capacités motrices. Ces données sont conformes à de nombreuses études postérieures
signalant une amĂ©lioration des aptitudes physiques, de la vitesse et de lâendurance chez
des sujets jeunes traités par des UV ou par des suppléments contenant de la vitamine D.
Des observations complĂ©mentaires font Ă©tat dâun effet significatif sur la force
musculaire, en particulier au niveau des membres inférieurs. Concernant les mécanismes mis
en jeu, certaines études fondamentales récentes ont montré que la vitamine D exerce des
effets moléculaires au sein de la cellule musculaire. Précisément, une action régulatrice
de la vitamine D sur les flux de calcium, lâhomĂ©ostasie minĂ©rale et certaines voies de
signalisation contrĂŽlant lâanabolisme protĂ©ique a Ă©tĂ© rapportĂ©e au niveau du tissu
musculaire. Plusieurs enquĂȘtes Ă©pidĂ©miologiques rĂ©vĂšlent quâun faible statut en vitamine D
est toujours associé à une diminution de la masse, de la force et des capacités
contractiles musculaires chez la personne ùgée. Cette atteinte aboutit à une accélération
de la perte musculaire avec lâĂąge (sarcopĂ©nie), et par consĂ©quent Ă une rĂ©duction des
capacitĂ©s physiques et Ă une augmentation du risque de chute et de fracture. Ă lâinverse,
un apport supplémentaire de vitamine D chez le sujet ùgé améliore significativement les
paramÚtres fonctionnels musculaires classiquement recherchés
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