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The anabolic response to a meal containing different amounts of protein is not limited by the maximal stimulation of protein synthesis in healthy young adults.
Kim, IY, Schutzler, S, Schrader, A, Spencer, HJ, Azhar, G, Ferrando, AA, Wolfe, RR
American journal of physiology. Endocrinology and metabolism. 2016;(1):E73-80
Abstract
We have determined whole body protein kinetics, i.e., protein synthesis (PS), breakdown (PB), and net balance (NB) in human subjects in the fasted state and following ingestion of ~40 g [moderate protein (MP)], which has been reported to maximize the protein synthetic response or ~70 g [higher protein (HP)] protein, more representative of the amount of protein in the dinner of an average American diet. Twenty-three healthy young adults who had performed prior resistance exercise (X-MP or X-HP) or time-matched resting (R-MP or R-HP) were studied during a primed continuous infusion of l-[(2)H5]phenylalanine and l-[(2)H2]tyrosine. Subjects were randomly assigned into an exercise (X, n = 12) or resting (R, n = 11) group, and each group was studied at the two levels of dietary protein intake in random order. PS, PB, and NB were expressed as increases above the basal, fasting values (mg·kg lean body mass(-1)·min(-1)). Exercise did not significantly affect protein kinetics and blood chemistry. Feeding resulted in positive NB at both levels of protein intake: NB was greater in response to the meal containing HP vs. MP (P < 0.00001). The greater NB with HP was achieved primarily through a greater reduction in PB and to a lesser extent stimulation of protein synthesis (for all, P < 0.0001). HP resulted in greater plasma essential amino acid responses (P < 0.01) vs. MP, with no differences in insulin and glucose responses. In conclusion, whole body net protein balance improves with greater protein intake above that previously suggested to maximally stimulating muscle protein synthesis because of a simultaneous reduction in protein breakdown.
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Consumption of Milk Protein or Whey Protein Results in a Similar Increase in Muscle Protein Synthesis in Middle Aged Men.
Mitchell, CJ, McGregor, RA, D'Souza, RF, Thorstensen, EB, Markworth, JF, Fanning, AC, Poppitt, SD, Cameron-Smith, D
Nutrients. 2015;(10):8685-99
Abstract
The differential ability of various milk protein fractions to stimulate muscle protein synthesis (MPS) has been previously described, with whey protein generally considered to be superior to other fractions. However, the relative ability of a whole milk protein to stimulate MPS has not been compared to whey. Sixteen healthy middle-aged males ingested either 20 g of milk protein (n = 8) or whey protein (n = 8) while undergoing a primed constant infusion of ring (13)C₆ phenylalanine. Muscle biopsies were obtained 120 min prior to consumption of the protein and 90 and 210 min afterwards. Resting myofibrillar fractional synthetic rates (FSR) were 0.019% ± 0.009% and 0.021% ± 0.018% h(-1) in the milk and whey groups respectively. For the first 90 min after protein ingestion the FSR increased (p < 0.001) to 0.057% ± 0.018% and 0.052% ± 0.024% h(-1) in the milk and whey groups respectively with no difference between groups (p = 0.810). FSR returned to baseline in both groups between 90 and 210 min after protein ingestion. Despite evidence of increased rate of digestion and leucine availability following the ingestion of whey protein, there was similar activation of MPS in middle-aged men with either 20 g of milk protein or whey protein.
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The in vivo TRPV6 protein starts at a non-AUG triplet, decoded as methionine, upstream of canonical initiation at AUG.
Fecher-Trost, C, Wissenbach, U, Beck, A, Schalkowsky, P, Stoerger, C, Doerr, J, Dembek, A, Simon-Thomas, M, Weber, A, Wollenberg, P, et al
The Journal of biological chemistry. 2013;(23):16629-16644
Abstract
TRPV6 channels function as epithelial Ca(2+) entry pathways in the epididymis, prostate, and placenta. However, the identity of the endogenous TRPV6 protein relies on predicted gene coding regions and is only known to a certain level of approximation. We show that in vivo the TRPV6 protein has an extended N terminus. Translation initiates at a non-AUG codon, at ACG, which is decoded by methionine and which is upstream of the annotated AUG, which is not used for initiation. The in vitro properties of channels formed by the extended full-length TRPV6 proteins and the so-far annotated and smaller TRPV6 are similar, but the extended N terminus increases trafficking to the plasma membrane and represents an additional scaffold for channel assembly. The increased translation of the smaller TRPV6 cDNA version may overestimate the in vivo situation where translation efficiency may represent an additional mechanism to tightly control the TRPV6-mediated Ca(2+) entry to prevent deleterious Ca(2+) overload.
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Post-exercise protein synthesis rates are only marginally higher in type I compared with type II muscle fibres following resistance-type exercise.
Koopman, R, Gleeson, BG, Gijsen, AP, Groen, B, Senden, JM, Rennie, MJ, van Loon, LJ
European journal of applied physiology. 2011;(8):1871-8
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Abstract
We examined the effect of an acute bout of resistance exercise on fractional muscle protein synthesis rates in human type I and type II muscle fibres. After a standardised breakfast (31 ± 1 kJ kg(-1) body weight, consisting of 52 Energy% (En%) carbohydrate, 34 En% protein and 14 En% fat), 9 untrained men completed a lower-limb resistance exercise bout (8 sets of 10 repetitions leg press and leg extension at 70% 1RM). A primed, continuous infusion of L: -[ring-(13)C(6)]phenylalanine was combined with muscle biopsies collected from both legs immediately after exercise and after 6 h of post-exercise recovery. Single muscle fibres were dissected from freeze-dried biopsies and stained for ATPase activity with pre-incubation at a pH of 4.3. Type I and II fibres were separated under a light microscope and analysed for protein-bound L: -[ring-(13)C(6)]phenylalanine labelling. Baseline (post-exercise) L: -[ring-(13)C(6)]phenylalanine muscle tissue labelling, expressed as (∂(13)C/(12)C), averaged -32.09 ± 0.28, -32.53 ± 0.10 and -32.02 ± 0.16 in the type I and II muscle fibres and mixed muscle, respectively (P = 0.14). During post-exercise recovery, muscle protein synthesis rates were marginally (8 ± 2%) higher in the type I than type II muscle fibres, at 0.100 ± 0.005 versus 0.094 ± 0.005%/h, respectively (P < 0.05), whereby rates of mixed muscle protein were 0.091 ± 0.005%/h. Muscle protein synthesis rates following resistance-type exercise are only marginally higher in type I compared with type II muscle fibres.
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Protein modification responds to exercise intensity and antioxidant supplementation.
Lamprecht, M, Oettl, K, Schwaberger, G, Hofmann, P, Greilberger, JF
Medicine and science in sports and exercise. 2009;(1):155-63
Abstract
PURPOSE To assess the effects of different exercise intensities and antioxidant supplementation on plasma protein modification. METHODS Trained men (n = 41) from a homogenous population were randomly assigned to perform cycle ergometer exercise either at 70% or 80% of individual .VO2max. Each intensity group was randomly assigned to receive either juice powder concentrate (JPC 70%, n = 11; JPC 80%, n = 10) or placebo (Plac 70%, n = 10; Plac 80%, n = 10) capsules for 28 wk. Four controlled exercise bouts and blood collections were conducted at baseline and study weeks 4, 16, and 28. Blood samples were drawn before (BE), immediately after (IE), and 30 min (30M) and 30 h (30H) postexercise. These samples were analyzed to estimate concentrations of carbonyl groups on plasma proteins (CP) and the redox state of human serum albumin (HSA). RESULTS In the Plac group, CP concentrations increased at 80% of .VO2max IE and 30M, returning to preexercise concentrations by 30H (P < 0.05). At both 16 and 28 wk, the Plac groups had significantly higher BE and 30H CP concentrations than the JPC groups (P < 0.05). The reduced fraction of HSA, human mercaptalbumin (HMA), decreased at all four exercise tests at both exercise intensities IE and 30M, returning to preexercise values by 30H (P < 0.05). Supplementation had no influence on HSA. CONCLUSIONS These results indicate that CP concentrations increase with 80% .VO2max intensity. The JPC group had lower baseline CP levels after 16 and 28 wk and no exercise-induced CP increase. HSA is reversibly shifted to a more oxidized state by recent intense exercise.
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Changes in skeletal muscle protein metabolism and myosin heavy chain isoform messenger ribonucleic acid abundance after treatment of hyperthyroidism.
Brennan, MD, Coenen-Schimke, JM, Bigelow, ML, Nair, KS
The Journal of clinical endocrinology and metabolism. 2006;(11):4650-6
Abstract
BACKGROUND Hyperthyroidism causes a hypermetabolic state and skeletal muscle dysfunction, but the underlying mechanism remains incompletely defined. OBJECTIVE The objective of the study was to determine whether treatment of hyperthyroidism causes changes in amino acid fluxes, synthesis rates of muscle proteins, and expression of muscle myosin heavy chain (MHC) that may impact skeletal muscle function and metabolic rate. METHODS Eight hyperthyroid patients were studied (TSH 0.008 +/- 0.001 mU/liter) before treatment and at least 9 months after correction of hyperthyroidism (TSH 2.3 +/- 0.4) (P < 0.03). Fluxes of leucine and phenylalanine as well as muscle protein synthesis rates were measured using L[1,2 13C] leucine and L(15N) phenylalanine as tracers. mRNA levels of selected genes were measured in muscle biopsy samples. RESULTS Treatment decreased resting metabolic rate that paralleled changes in fluxes of leucine and phenylalanine accompanied by improved muscle strength and mass. Synthesis rates of mixed muscle proteins (P = 0.01), sarcoplasmic (P = 0.04), and mitochondrial (P = 0.08) proteins decreased, whereas MHC synthesis was unchanged. Selective increases in mRNA abundance of muscle MHC1 isoform (P = 0.04) and decrease of MHCIIA (P = 0.007) and MHCIIx (P = 024) were observed. Muscle mitochondrial oxidative enzymes and mRNA levels of mitochondrial proteins were unchanged, but uncoupling protein2 and uncoupling protein3 mRNA levels (P = 0.02) decreased. CONCLUSION Increased amino acid flux, mixed muscle protein synthesis, and synthesis of sarcoplasmic proteins are consistent with the hypermetabolic state in hyperthyroidism. After treatment, MHC synthesis rates were unchanged, but mRNA levels of isoforms of MHC found in slow-twitch and fast-twitch fibers increased and decreased, respectively. These results offer a mechanistic explanation for posttreatment improvement in muscle functions in hyperthyroidism.