Paulette Rousset

Synergistic effects of caloric restriction with maintained protein intake on skeletal muscle performance in 21-month-old rats: a mitochondria-mediated pathway

Caloric restriction (CR) delays the onset of age‐related mitochondrial abnormalities but does not prevent the decline in ATP production needed to sustain muscle protein fractional synthesis rate (FSR) and contractile activity. We hypothesized that improving mitochondrial activity and FSR using a CR diet with maintained protein intakes could enhance myofibrillar protein FSR and consequently improve muscle strength in aging rats. Wistar rats (21 months old) were fed either an ad libitum (AL), 40% protein‐energy restricted (PER) or 40% AL‐isonitrogenous energy restricted (ER) diet for 5 months. ATP production, electron transport chain activity, reactive oxygen species (ROS) generation, protein carbonyl content and FSR were determined in both tibialis anterior (TA) and soleus muscle mitochondria. Myosin and actin FSR and grip force were also investigated. The ER diet led to improved mitochondrial activity and ATP production in the TA and soleus muscles in comparison with PER. Furthermore, mitochondrial FSR in the TA was enhanced under the ER diet but diminished under the PER. Mitochondrial protein carbonyl content was decreased by both the ER and PER diets. The ER diet was able to improve myosin and actin FSR and grip force. Therefore, the synergistic effects of CR with maintained protein intake may help to limit the progression of sarcopenia by optimizing the turnover rates and functions of major proteins in skeletal muscle.—Zangarelli, A., Chanseaume, E., Morio, B., Brugère, C., Mosoni, L., Rousset, P., Giraudet, C., Patrac, V., Gachon, P., Boirie, Y., Walrand, S. Synergistic effects of caloric restriction with maintained protein intake on skeletal muscle performance in 21‐month‐old rats: a mitochondria‐mediated pathway. FASEB J. 20, 2439–2450 (2006)

Mitochondrial and sarcoplasmic proteins, but not myosin heavy chain, are sensitive to leucine supplementation in old rat skeletal muscle

Leucine has a major anabolic impact on muscle protein synthesis in young as in old animals. However, myosin heavy chain (MHC), sarcoplasmic and mitochondrial proteins may differently respond to anabolic factors, especially during aging. To test this hypothesis, fractional synthesis rates (FSR) of the three muscle protein fractions were measured using a flooding dose of [1-(13)C] phenylalanine, in gastrocnemius muscle of adult (8 months) and old (22 months) rats, either in postabsorptive state (PA), or 90-120 min after ingestion of a alanine-supplemented meal (PP+A) or a leucine-supplemented meal (PP+L). In adult and old rats, in comparison with PA, leucine stimulated mitochondrial (adult: 0.260+/-0.011 vs 0.238+/-0.012%h(-1); old: 0.289+/-0.010 vs 0.250+/-0.010%h(-1); PP+L vs PA, P<0.05) and sarcoplasmic (adult: 0.182+/-0.011 vs 0.143+/-0.006%h(-1); old: 0.195+/-0.010 vs 0.149+/-0.008%h(-1); PP+L vs PA, P<0.05) protein FSR, but not MHC synthesis in old rats (0.101+/-0.009 vs 0.137+/-0.018%h(-1); PP+L vs PA, P=NS). In conclusion, synthesis of specific muscle protein is activated by leucine supplementation, but MHC may be less sensitive to anabolic factors with aging.

Chronological Approach of Diet-induced Alterations in Muscle Mitochondrial Functions in Rats

Objective: Mitochondrial dysfunction might predispose individuals to develop insulin resistance. Our objective was to determine whether mitochondrial dysfunction or insulin resistance was the primary event during high‐fat (HF) diet.

Higher calcium urinary loss induced by a calcium sulphate-rich mineral water intake than by milk in young women

It is well known that the intestinal availability of Ca from Ca-rich mineral waters is equivalent to that of milk Ca. However, the effect of associated anions on Ca urinary loss needs to be addressed. The aim of the current study was to compare, under ordinary conditions of consumption, milk and a SO4-rich mineral water as the Ca provider in a large number of subjects consuming the same quantity of Ca from the two sources in a crossover study lasting for an extended period. Thirty-seven healthy women completed a 12-week protocol, divided into four periods of 3 weeks (W). In the first (W1-3) and third (W6-9) periods, dietary Ca intake was restricted to 600 mg/d. In the second (W4-6) and final (W10-12) periods, either 400 ml/d medium-fat milk or 1 litre of a Ca- and SO4-rich mineral water, each providing about 480 mg Ca/d, was added to the diet in a random manner. Dietary evaluation, blood and urinary measures were performed during the last week (W6 and W12) of each Ca supplementation period. The urinary excretion of Ca was higher (0.5 mmol/d more) with water than with milk (P<0.001). An examination of all the dietary factors known to influence calciuria suggested that the acidogenic action of SO4 was responsible for this increased calciuria. Thus, despite an equal Ca intake and assuming an unchanged intestinal absorption, these results suggest that Ca balance is better with milk consumption than with CaSO4-rich water.

Effects of trans MUFA from dairy and industrial sources on muscle mitochondrial function and insulin sensitivity.

Epidemiological studies suggest that chronic consumption of trans MUFA may alter muscle insulin sensitivity. The major sources of dietary trans MUFA (dairy fat vs. industrially hydrogenated oils) have different isomeric profiles and thus probably different metabolic consequences. These effects may involve alterations in muscle mitochondrial oxidative capacity, which may in turn promote insulin resistance if fatty acid oxidation is reduced. We report that in Wistar rats, an 8 week diet enriched (4% of energy intake) in either dairy, industrial, or control MUFA did not alter insulin and glucose responses to an intraperitoneal glucose tolerance test (1g/kg). In C2C12 myotubes, vaccenic and elaidic acids did not modify insulin sensitivity compared with oleic acid. Furthermore, the ex vivo total, mitochondrial and peroxisomal oxidation rates of [1-14C]oleic, vaccenic, and elaidic acids were similar in soleus and tibialis anterior rat muscle. Finally, an 8 week diet enriched in either dairy or industrial trans MUFA did not alter mitochondrial oxidative capacity in these two muscles compared with control MUFA but did induce a specific reduction in soleus mitochondrial ATP and superoxide anion production (P < 0.01 vs. control). In conclusion, dietary trans MUFA of dairy or industrial origin have similar effects and do not impair muscle mitochondrial capacity and insulin sensitivity.

Enhanced Muscle Mixed and Mitochondrial Protein Synthesis Rates after a High-fat or High-sucrose Diet

Objective: Obesity and insulin resistance are associated with muscle mitochondrial dysfunction, which might be related to impairment of mitochondrial protein synthesis. This study aimed at investigating mixed and mitochondrial protein synthesis in skeletal muscle in response to dietary manipulations.

Fast proteins with a unique essential amino acid content as an optimal nutrition in the elderly: growing evidence.

BACKGROUND & AIMS Adequate protein intake is crucial to maintain body protein content in elderly subjects, but quality of dietary proteins should be also considered since amino acid composition and rate of protein digestion modulate amino acid availability. This study investigates whether the efficacy of optimal protein intake levels for protein retention in the elderly is influenced by protein quality. METHODS We investigated the effect of a 10-day adequate-protein (AP) or high-protein (HP) diet together with the protein source as caseins (CAS) or soluble milk proteins (PRO) on whole-body (WB) protein synthesis (PS) and protein breakdown (PB) in 4 groups of healthy elderly men (mean ± SEM: 71.8 ± 24.4 yr). The study consisted of two periods of 4 h each: a post-absorptive period and a postprandial period. The fed state was defined by consumption every 20 min and for 4 h, of either 15 g or 30 g of PRO or CAS. Steady-state WB and splanchnic leucine kinetics were measured using a continuous infusion of L-[1-13C]leucine in the postabsorptive state and L-[1-13C]leucine infusion plus oral L-[5,5,5-2H3]leucine in the postprandial state. RESULTS WB PS was stimulated by feeding only with HP diets, whereas WB PB corrected for splanchnic extraction showed a similar pattern of post-feeding decrease in all groups. Consequently, net leucine balance was greater in the postprandial state after HP meals than after AP meals, with PRO meals leading to a better postprandial leucine balance (3.63 ± 0.16 μmol kg FFM(-1) min(-1)vs. 2.77 ± 0.21 μmol kg FFM(-1) min(-1) for PRO HP and CAS HP, respectively; P = 0.005). CONCLUSION Postprandial protein retention was better improved in elderly men by an increase in protein intake when the protein supplementation was provided as fast-digesting proteins that induce high leucine availability.

P83 Effet de la surnutrition lipidique sur la réaction inflammatoire et l’insulino-sensibilité du rat âgé : conséquences sur la synthèse protéique musculaire

Introduction L’insulino-resistance (IR) associee a l’obesite et au vieillissement, pourrait participer a l’acceleration des anomalies fonctionnelles au niveau musculaire, debouchant ainsi sur la mise en place d’une obesite sarcopenique. En effet, il a ete montre que l’insuline augmente les vitesses de synthese proteique (FSR) musculaire. L’objectif etait d’evaluer, chez le rat jeune ou âge l’effet de l’accroissement de l’adiposite par un regime hyper-lipidique et hyper-calorique (HL), sur la production de cytokines pro-inflammatoires, l’insulino-sensibilite (IoS) et la vitesse de synthese des proteines musculaires. Materiels et methodes 34 rats âges de 6 (J) ou 25 (V) mois repartis en 4 groupes, ont recu un regime normo-lipidique (JNL, VNL) ou HL (JHL, VHL) durant 10 semaines. L’inflammation, la sensibilite a l’insuline ainsi que les FSR musculaires ont ete mesurees. Resultats Le regime HL a entraine une moindre augmentation (p vs VNL) comparativement au rat jeune (+ 80 % ; p vs JNL). L’IR et le statut inflammatoire sont augmentes dans le groupe VHL (VHL vs VNL, JNL, JHL ; p vs VNL ; p Conclusion Le regime HL a donc induit une inflammation et une insulinoresistance uniquement chez le rat âge, entrainant une reduction de la proteosynthese musculaire. Il nous reste a caracteriser les dysfonctionnements du tissu adipeux chez le vieux rat et leurs roles dans le dialogue entre le muscle squelettique et ce tissu.

O006 L’apport calorique hyper-lipidique favorise l’insulino-résistance et l’inflammation et réduit la synthèse protéique musculaire chez le rat âgé

Introduction et but de l’etude Le vieillissement est caracterise par une accumulation et une redistribution de la masse grasse corporelle avec une augmentation importante des depots adipeux intra-abdominaux. Ce phenomene pourrait contribuer aux perturbations de l’accretion proteique musculaire liees a l’âge, en particulier chez le sujet âge obese, debouchant sur le syndrome d’obesite sarcopenique. L’objectif de cette etude etait d’evaluer, chez le rat jeune ou âge, l’effet de l’accroissement de l’adiposite par un regime hyper-lipidique et hyper-calorique (HL), sur la production de cytokines pro- et anti-inflammatoires, l’insulino-sensibilite (IoS) et la vitesse de synthese des proteines musculaires et adipeuses (FSR). Materiel et methodes 34 rats Wistar mâles âges de 6 (J) ou 25 (V) mois ont ete repartis en 4 groupes et ont recu un regime normo-(JNL, VNL) ou hyper-lipidique/hyper-calorique (JHL, VHL) durant 10 semaines. Un test de tolerance au glucose (IPGTT) a ete realise afin d’evaluer l’IoS. Le profil inflammatoire a ete evalue en mesurant la concentration plasmatique (ELISA) du recepteur soluble du TNFa (sTNF-R2) et la quantite d’ARNm (qRT-PCR) de l’adiponectine dans le tissu adipeux. Le FSR a ete calcule a partir de l’enrichissement en [13C] valine des proteines musculaires (tibialis anterior) et adipeuses (tissu adipeux abdominal) par spectrometrie de masse. Resultats L’IoS etait diminuee chez les vieux rats soumis a un regime HL (VHF vs VNL, JNL, JHF ; p Conclusions L’augmentation de l’adiposite chez les rats âges induite par le regime HL s’accompagne d’une augmentation de l’inflammation, d’une insulinoresistance, et d’une reduction de la synthese proteique musculaire. Ce defaut d’adaptation du metabolisme proteique preferentiellement musculaire en reponse au regime HL pourrait participer a l’acceleration de la perte proteique musculaire et favoriser l’apparition d’une obesite sarcopenique.

Higher calcium urinary loss induced by a calcium sulphate-rich mineral water intake than by milk in young women â reply by Brandolini et al.

It is well known that the intestinal availability of Ca from Ca-rich mineral waters is equivalent to that of milk Ca. However, the effect of associated anions on Ca urinary loss needs to be addressed. The aim of the current study was to compare, under ordinary conditions of consumption, milk and a SO4-rich mineral water as the Ca provider in a large number of subjects consuming the same quantity of Ca from the two sources in a crossover study lasting for an extended period. Thirty-seven healthy women completed a 12-week protocol, divided into four periods of 3 weeks (W). In the first (W1-3) and third (W6-9) periods, dietary Ca intake was restricted to 600 mg/d. In the second (W4-6) and final (W10-12) periods, either 400 ml/d medium-fat milk or 1 litre of a Ca- and SO4-rich mineral water, each providing about 480 mg Ca/d, was added to the diet in a random manner. Dietary evaluation, blood and urinary measures were performed during the last week (W6 and W12) of each Ca supplementation period. The urinary excretion of Ca was higher (0.5 mmol/d more) with water than with milk (P<0.001). An examination of all the dietary factors known to influence calciuria suggested that the acidogenic action of SO4 was responsible for this increased calciuria. Thus, despite an equal Ca intake and assuming an unchanged intestinal absorption, these results suggest that Ca balance is better with milk consumption than with CaSO4-rich water.