Leucine Incorporation Into Mixed Skeletal Muscle Protein In Humans

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Measurement of Muscle Protein Synthesis by Positron Emission

Therefore, most of the radioactivity that is retained in skeletal muscle following a dose of [11C]methionine can be taken as an index of its incorporation into proteins. Also, for muscle, in contrast to some other 11C-labeled tracers, such as [1-11C]leucine, analysis of PET studies with [11C]methionine is

Leucine-enriched essential amino acids attenuate muscle

effect of LEAAs on the rate of muscle protein synthesis after ECs in rats. The tibialis anterior (TA) muscle of rats was forced to contract by electrical stimulation. The frac-tional synthesis rate (FSR; %/h) was determined by calcu-lating the incorporation rate of L-[ring-2H 5] phenylalanine into the skeletal mixed muscle protein pool. Muscle

Muscle protein synthesis in response to nutrition and exercise

of amino acids captured from dietary protein sources, into skeletal muscle proteins. The purpose of this is to compensate for muscle protein that is lost in fasted (postabsorptive) periods due to, for example, amino acid oxidation and/or carbon donation for liver gluconeogenesis (Wackerhage & Rennie, 2006). Critically

Increased rates of muscle protein turnover and amino acid

The leucine tracer incorporation technique has shown that the rate of muscle protein synthesis in humans is increased after exercise (6, 7) and remains elevated for > 24 h (7). In these studies, muscle protein break- down was not directly measured. However, the increase

Bond University Research Repository Effects of acute oral

Effects of acute oral feeding on protein metabolism and muscle protein synthesis in people with cancer Running head Metabolic effects of acute oral feeding in cancer Barbara S van der Meij PhD RD1,2,3 Lynette M De Groot APD 2,3. Nicolaas EP Deutz PhD MD4. Mariëlle PKJ Engelen PhD. 4

Fast Dairy NUTRITION Nutrition

of muscle protein turnover and amino acid transport after resistance exercise in humans. The American Journal of Physiology, 268, E514 E520. Biolo G, Tipton K D, Klein S & Wolfe R R (1997). An abundant supply of amino acids enhances the metabolic effect of exercise on muscle protein. The American Journal of Physiology, 273, E122 E129.

Soy-dairy protein blend and whey protein ingestion after

Sep 30, 2013 transport into muscle. We hypothesized that the prolonged hyperaminoacidemia from ingesting a blend of proteins would reduce markers of protein breakdown and enhance overall skeletal muscle protein anabolism, myofibrillar protein synthe-sis, amino acid transport into muscle, and amino acid trans-porter expression compared with the ingestion of

Nutrition & Metabolism BioMed Central

observed in humans during fasting, leucine incorporation into skeletal muscle showed a significant increase (5 to 17%). Growth hormone (GH) GH has a major role in regulating growth and develop-ment. GH is a protein anabolic hormone and it stimulates muscle protein synthesis. As low blood sugar increases GH secretions, one could speculate that a

Mechanisms of Postprandial Protein Accretion in Human

postprandial protein turnover occurring in skeletal muscle, i.e., the most abundant deposit of body proteins (12), have been scarcely investigated in humans. Studies performed using tracer amino acid(s) incorporation into mixed skeletal muscle proteins through needle biopsy, have shown either a stimula-


skeletal muscle to potent anabolic stimuli such as amino acids and insulin. The mechanism most commonly proposed to explain this indirect priming action of O3FA in stimulating MPS involves the direct incorporation of O3FA into the phospholipid membrane of skeletal muscle. Consistent with this idea, a recent study reported an ~100%

Effect of beta-hydroxybutyrate on whole-body leucine kinetics

Leucine flux during beta-OHB infusion did not differ from leucine flux during normal saline infusion in nine normal subjects, whereas leucine oxidation decreased 18-41% (mean = 30%) from 18.1 +/- 1.1 mumol.kg-1.h-1 (P less than 0.01), and incorporation of leucine into skeletal muscle protein increased 5-17% (mean =

Metabolism of Branched-Chain Amino Acids in Starved Rats: The

decrease in leucine appearance from proteolysis, leucine incorporation into body proteins, leucine oxidation, leucine-oxidized fraction, and leucine clearance. Protein synthesis decreased significantly in skeletal muscle and the liver. There were no significant differences in leucine and KIC oxidation by IPL.

The Leucine Content of a Complete Meal Directs Peak

We assessed fractional rates of protein synthesis (FSR) from the rate of incorporation of L-[2H 5]phenylalanine into total mixed muscle protein as described previously (8). The time from injection of the metabolic tracer until tissue cooling was recorded as the actual time for L-[2H a peak activation.

Impaired anabolic response of muscle protein synthesis is

effect of nutrients on mixed-muscle protein synthesis in adult rats is not observed in old rats (7, 8). In addition, the stimulation of muscle protein synthesis in response to combined hyperaminoacidemia and glucose is also impaired in elderly subjects (9). These observations are D Page 1 of 16 (page number not for citation purposes)

doi:10.1093/gerona/gls141 10.1093/gerona/gls141 Muscle

(8,17). Incorporation of [1,2-13C 2]leucine into protein was determined by gas chromatography combustion isotope ratio mass spectrometry (Delta plus XP, Thermofisher Scientific, Hemel Hempstead, UK) using our standard techniques (18). The fractional synthesis rate (FSR) of myofibrillar protein was determined from the incorporation of [1,2-13C 2

The mTORC1 signaling repressors REDD1/2 are rapidly induced

Aug 10, 2012 Measurement of skeletal muscle protein synthesis. Skeletal muscle protein synthesis was measured by the incorporation of puromycin into peptide chains as described (20). Briefly, immunoblot membranes were incubated and rocked overnight at 4°C with a mouse monoclonal anti-puromycinantibodygeneratedin-house(1 g/mlinTris-buffered saline).

The Journal of Physiology - Wiley

maintenance of skeletal muscle mass. Much work has been undertaken, over several years, in identifying anabolically active nutrients for skeletal muscle. Early experiments using stable isotope tracer techniques in humans showed that feeding a mixed macronutrient meal approximately doubled rates of MPS (Rennie et al. 1982). Subsequent studies

A multifactorial anti-cachectic approach for cancer cachexia

tic TB rats caused increased incorporation of orally adminis-tered labelled 14C-leucine into muscle protein, without altering the in vivo rate of the amino acid oxidation, sugges-ting that MA treatment is able to increase protein synthesis during cancer cachexia. With regard to finding a pharmacological strategy to coun-

Leucine metabolism in rats with cirrhosis

leucine intake is zero in our protocol, leucine turnover estimates the leucine released from protein. These par- ameters of leucine metabolism may be calculated from the following equation: Q=In+D=B (+E). On the basis of this equation, the incorporation of leucine into protein, the oxidized fraction of leucine and the fraction of leucine

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in anterior tibialis muscle protein synthesis in healthy man during mixed amino acid infusion: studies of incorporation of [1-13C] leucine. Clinical Science (London, England: 1979), 76, 447 454. Biolo G, Maggi S P, Williams B D, Tipton K D & Wolfe R R (1995). Increased rates

Contents lists available at ScienceDirect Clinical Nutrition

Skeletal muscle Protein Resistance exercise Metabolism summary Skeletal muscle is the largest organ of the human body and plays a pivotal role in whole-body homeostasis through the maintenance of physical and metabolic health. Establishing strategies aimed at increasing the amount, and minimising loss, of muscle mass are of upmost importance.

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monly occur in both humans and animals. Weight loss is seen in many cancer patients (1) and is associated with reductions in skeletal muscle protein synthesis (2). To further understand the alterations in protein metabolism in cancer, we examined the effect of two different cancers on whole body, muscle, and liver protein synthesis.

TESI COMPLETA 2 - units.it

Skeletal muscle is the major body site of protein metabolism, being the largest tissue in the body (Shils ME et al. 2006; Caballero B et al. 2012). Muscle protein synthesis (MPS) is influenced by AA availability after the intake of a meal containing proteins. The post-prandial anabolic response is followed in the post-absorptive period, by a

Effect of whey protein isolate on strength, body composition

Leucine is an established modulator of muscle protein metabolism and has been identified as a key regulator in the translation initiation pathway of muscle protein synthesis [35]. The importance of a leucine rich diet to promote muscle anabolism, healthy blood glucose metabolism and the management of a healthy weight are now recognized [36].

Measurement emission L-[methyl-1 C]methionine

skeletal muscle. The model assumes that transamination and trans-methylation are negligible andcontainsvascular space, tissue precur-sor, and protein compartments. The rate constants k1,2 and k2,1 represent forward and reverse transport of methionine between plasma and tissue, and k2,3 represents incorporation into proteins. Proc. Natl. Acad


food intake has also been investigated in skeletal muscle protein synthesis. Welle et al. (1994) showed no difference in whole-body incorporation of leucine into proteins in the young. However, the fractional myofibrillar protein synthesis in the vastus lateralis muscle was 28% slower in the older group. In rats, Mosoni et

Cell Metabolism Review

Protein Flux between Gut, Splanchnic Tissue, and Skeletal Muscle during Postabsorptive, Postprandial, and Insulin-Deficient States (A) In the nondiabetic postabsorptive (fasting) state, protein degradation (PD) exceeds protein synthesis (PS) in the muscle, leading to efflux of amino acids into

and recommendations for athletes and active populations

acid catabolism and muscle protein building at rest, during exercise and during the recovery period after a single experiment or training sessions. Stable isotopic tracers (13. C-lysine, 15. N-glycine, 2. H. 5-phenylalanine) and arteriovenous differences have been used in studies of skeletal muscle and collagen tissues under resting and


Myotube Protein Synthesis and Protein Degradation [3H]Leucine (120 Ci/mmol) and [3H]tyrosine (40 Ci/mmol) were obtained from ARC. For analysis of protein synthesis, [3H]leucine incorporation into cultured myotubes was deter-minedasdescribedpreviously (30). Protein degradation assays were performed according to a previously described protocol

Research Article Human skeletal muscle is refractory to the

Human skeletal muscle is refractory to the anabolic effects of leucine during the postprandial muscle-full period in older men W. Kyle Mitchell1,2, Bethan E. Phillips1, Ian Hill3, Paul Greenhaff3, Jonathan N. Lund2, John P. Williams2, Debbie Rankin1, Daniel J. Wilkinson1, Kenneth Smith1 and Philip J. Atherton1

Rapid aminoacidemia enhances myofibrillar protein synthesis

after a period of tracer incorporation (12, 28 32). This method assumes that the 13C enrichment of a mixed plasma protein fraction reflects the 13C enrichment of the muscle protein (33). To minimize the number of biopsies taken, we obtained a single resting biopsy (trial 1 only) that was used to calculate a baseline rate of MPS.

Altered Leucine Metabolism in Noncachectic Sarcoma Patients

incorporation into protein (protein synthesis); C, the rate of leucine oxidation (or catabolismi; li. the rate of leucine release from protein (protein breakdown); and /, the rate of exogenous leucine intake. Leucine turnover is measured from the dilution of [l-'3C]leucine in plasma leucine once isotopie steady state is reachedfl-lf-l (2)