* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Protein
Basal metabolic rate wikipedia , lookup
Clinical neurochemistry wikipedia , lookup
Paracrine signalling wikipedia , lookup
Artificial gene synthesis wikipedia , lookup
Ribosomally synthesized and post-translationally modified peptides wikipedia , lookup
Gene expression wikipedia , lookup
G protein–coupled receptor wikipedia , lookup
Biosynthesis wikipedia , lookup
Genetic code wikipedia , lookup
Amino acid synthesis wikipedia , lookup
Expression vector wikipedia , lookup
Point mutation wikipedia , lookup
Magnesium transporter wikipedia , lookup
Homology modeling wikipedia , lookup
Ancestral sequence reconstruction wikipedia , lookup
Biochemistry wikipedia , lookup
Metalloprotein wikipedia , lookup
Interactome wikipedia , lookup
Bimolecular fluorescence complementation wikipedia , lookup
Western blot wikipedia , lookup
Nuclear magnetic resonance spectroscopy of proteins wikipedia , lookup
Protein purification wikipedia , lookup
Protein–protein interaction wikipedia , lookup
Protein and amino acids Proteins • Contain C, H, O, N and some have S, Fe, P, Co • Long chains of amino acids • 20 amino acids • Fairly water sol • Essential and nonessential (12) Amino acids • Non-essential – – – – – – – – – – – – Alanine Arginine (ess in children) Asparagine Aspartate Cysteine Glutamate Glutamine (ess in children) Glycine Proline Serine Tyrosine Histidine (ess in infants) • Essential – – – – – – – – Isoleucine Leucine Lysine Methionine Phenylalanine Threonine Tryptophan Valine Peptide bonds • 2 amino acids linked by dehydration • Results in covalent bond between amino gp and carboxylic gp • Results in peptides • (Dipeptides - polypeptides) • Negatively charged in solution 7 essential functions • • • • • • • Support Movement Transport Buffering Metabolic regulation Coordination & control Defense Amino acid metabolism Protein Intake • Not associated with Western diseases of affluence • Protein deficiency uncommon in developed world • RDA varies ~0.8 g/kg bw • Intake usually ~80-100g/day, 10 – 15% total energy intake • Sources – meat/fish – complete protein • Grains, legumes - incomplete Sources of protein in the British Diet. >60% from animal products How is protein metabolism studied? • Eg. – Urea concentration in urine and sweat; – N balance = Nt – Nu – Nf – Ns = 0 • +ve N balance – in children, pregnancy, during resistance training • -ve N balance – Lack of other energy nutrients (Butterfield, 1987); DM; fever, burns, dieting/starvation – Isotopes – radiolabeled or stable (3H, or 13C) – Tracer incorporation/release into/from a specific protein – Leucine oxidation N-balance • Protein breakdown generally increases modestly with exercise; • Protein synthesis rises substantially following endurance and resistance exercise • idea that protein intake might be higher in sport – Due to increased breakdown during training; – Due to increased synthesis in recovery period – eg. new myofibrils or mitochondria • Is N-balance relevant to athletes? Muscle size, strength, oxidative capacity Net Protein Balance (NPB) • Rest/fasted state – NPB –ve (ie. B’down > synth) • After exercise in fasted state – Both synth and b’down ↑, NPB still –ve but less so than rest as ↑ synth> ↑ b’down • Eating CHO/αα before/immediately post ex – ↑ αα availability & transport into cell, counteracts catabolic state & ↑protein synth – ↓b’down – +ve NPB Contribution to energy • At rest contributes between 5 – 15% – Decreases in exercise due to CHO and fat – Prolonged endurance may contribute up to 10% - via alanine – glucose cycle. • Controversy – 2 camps – Those who believe sport ↑ protein req • Lemon et al., Tarnopolsky et al. – Those who believe req are not different to sedentary people – increased efficiency use of αα • Butterfield et al., • Evidence for both – practically not often an issue – Few studies on protein intake and performance – Meta-analysis – protein supplements no impact on muscle mass (Nissen and Sharp, 2003) Protein and resistance • Suggested increased requirements are related to requirement for muscle hypertrophy • After resistance exercise muscle protein turnover is increased due to increase in synthesis and breakdown (breakdown to a lesser degree) • Increased protein requirements are controversial – many short studies – when start training see –ve N balance – but reversed within 12 days of training • Recommendation is 1.6 – 1.7 g/kg bw, acceptable range 20 – 40% (max) – Again often met by a normal diet. • Tarnopolsky et al. (1992) found intake of 2.4g/kg/d was no more effective than 1.4g/kg/d in permitting strength and weight gain Protein and resistance – amino acid supplements • Amino acid supplements touted as way of increasing GH, insulin anabolism – but no evidence to support if protein consumption > 2g/kg/d. • Supplements of individual amino acids popular in certain circles in attempt to stimulate release of growth hormone and insulin eg. Arginine – High doses of arginine, ornithine and lysine may increased levels of GH and insulin but no effect on LBM or muscle function (Merimee et al., 1969) • However studies showing hormonal effect used 30g amino acids, cf. 1-2g/day in typical supplements – which have failed to show an effect • Effect due to large doses still < effect of 60min moderate exercise Protein and resistance – CHO and/or energy • CHO and protein taken together (ie. As in balanced diet) hormonal state favouring net protein synthesis (Rasmussen et al., 2000) – Carbohydrate inhibit muscle protein breakdown, but not stimulate synthesis – Also restores glycogen stores. • Testosterone secretion is optimal when protein:CHO ratio is 1:4 (ie. 15%:60% as in balanced diet) Volek et al., (1997) • If an overall energy deficit exists (due to heavy training/dieting) then –ve N balance will occur even if protein intake is 2x RDA. • Gater et al., (1992) – Resistance training for 10 weeks on one of 3 diets • No additions to normal diet • Amino acid supplement • +ve energy balance – Greatest gains in lbm with +ve energy balance Volek, et al., Testosterone and cortisol in relationship to dietary nutrients and resistance exercise. J. Appl. Physiol. 82(1): 4954, 1997. i.e. “balanced diet” optimal for maintenance of teatosterone levels. Source of protein • Which protein or amino acid most effective at post-exercise anabolism? • Tipton et al. (2004) no difference in NPB after post-ex ingestion of casein or whey • Koopman et al., (2005) – no difference casein hydrolysate with or without leucine • Wilkerson et al., (2006) milk protein > soy proteins • Interaction with other nutrients ingested and timing in relation to exercise. • More studies warranted. Protein and resistance – why not consume loads of protein? • Reduced CHO and fat intake – most imp. • Amino acids may cause GI distress due to osmotic effect • increased oxidation ie. Adapt and burn as metabolic fuel. • Excretion of urea requires dilution with water and so may contribute to dehydration • Excess protein catabolism results in urinary loss of Ca • Unknown whether ingestion of one effect on another nutritional imbalance. • No negative effects on kidney function Other factors • Impossible to maintain +ve N balance when in energy deficit • Complete vs. incomplete protein • Aa’s may be used preferentially by different tissues • Other nutrients ingested – Eg. CHO ↑ use of aa’s ingested concomitantly after resistance ex (insulin?) • Timing – although dependent on type of protein • i.e. consideration of only amount of protein is scratching the surface At risk groups • Those at risk of low energy (and thus low protein intake) – Amenorrheic female runners, male and female gymnasts, female dancers – Weight class athletes/wt loss program – Training camp (sudden ↑ training) – Vegetarian athletes? – lower quality protein, lower digestibility? – evidence lacking (Haub et al. 2002) • But possibly superior balance with reliance on animal protein Protein and Endurance • Exercise increases protein oxidation & N loss + synth mitochondrial enzymes • Equivocal evidence over whether endurance athletes need more protein • Training has protein sparing effect (McKenzie et al., 2000) • Those that do advocate increased protein – 1.2 – 1.4g/kg bw – This is usually easily met due to the increase in food intake in endurance athletes usually automatic increase in protein – Provided energy intake meets expenditure endurance athletes probably do not need to supplement with protein. • Under nutritional (low energy or CHO) or metabolic (intense training) stress can see increased oxidation • Studies consistently show higher oxidation in ♂ Protein and endurance • Protein intake during exercise – Suggested small amnt protein in sports drink can improve endurance capacity (Ivy et al., 2003; Saunders et al., 2004) • • – However rate CHO delivery was less than optimal – 37 – 47 g CHO/hr Drinks not matched for caloric content Van Essen et al., (2006) • Sports drink 60g CHO/hr • 80km tt – no difference – but both better than placebo – – – Romano-Ely et al., (2006) – no difference when matched for caloric content Saunders et al., (2006) 60g CHO/hr, + prot. • – – Increased oxidation – spare muscle glycogen etc; increased TCA intermediates; central fatigue fuel transport across intestine, increased insulin Muscle recovery? • – Saw improvement in late race time-trial performance Mechanism? • • • • • – 6% CHO, 6%CHO +2% whey, sweetened placebo Beneficial to protein balance, and attenuates post-exercise markers of muscle damage, and improves subsequent exercise. Saunders et al., (2007) – Coingestion of carbohydrate-protein during endurance exercise: influence on performance and recovery IJSNEM 17: S87 – S103 Seifert et al., (2006) adding protein (1.5%) to CHO-containing drink (6%) improved fluid retention Protein and endurance • Protein intake post exercise – Repair, synthesis muscle protein, synthesis muscle glycogen – Levenhagen et al. (2002) – protein + CHO postexercise facilitates uptake of amino acids. – However feeding of CHO at frequent intervals negates effects of additional protein (in terms of maximising glycogen stores – see CHO lecture) –only works when CHO intake is suboptimal BCAAs • Participate directly (fuel and prot synth), and indirectly (synth of neurotransmitters) – serotonin, dopamine and noradrenaline • Often added to energy drinks to provide additional fuel • However minor cf CHO and fat – and ingestion of CHO prevents increase in BCAA oxidation • Supplementation unnecessary Central Fatigue Hypothesis • Proposed 1987 as fatigue mechanism (Newsholme et al.) • In exercise FAs are mobilised and transported to muscles bound to albumin • The amino acid tryptophan is also transported bound to albumin at the same binding site. • Therefore as FAs increase in exercise, more tryptophan is released from albumin free tryptophan (fTRP) Central Fatigue Hypothesis - theory • BCAA and fTRP compete for carrier-mediated transport into the CNS – there TRP is converted to serotonin • Increased ratio of serotonin:dopamine associated with tiredness • In exercise muscle metabolism of BCAAs increases, decreasing plasma BCAA so transporters can carry more TRP to CNS • Ingestion of BCAA raises fTRP:BCAA and therefore reduces transport of fTRP into CNS Davis et al., (2000) Central Fatigue Hypothesis - theory • However studies ingesting TRP have not had any effects upon performance – Evidence in animals but not humans • Some support for ingesting TYR (for DA) – in stress related environments (Owasoyo et al. 1992) • Also lack of evidence for supplementing BCAAs – different in animals • Evidence for exercise in heat – Mittleman et al., (1998) – But not supported by Watson et al. (2004) or Cheuvront et al., (2004) Conclusion • Adequate energy is critical • If muscle hypertrophy is the primary goal then hyperenergetic diet may be the most important recommendation – Suggested that 35 - 40% of total energy as protein may be upper limit – any higher limits CHO and fat • Evidence that protein intake above RDA may be beneficial to athletes – but – Little research into maximum tolerable protein intake; – Xs protein increases Ca loss – No evidence for kidney harm Conclusion • Recommendations of 1.2 – 1.8 g/kg/d are common • Many high protein foods also high in fats (and food knowledge is not generally good in athletes) • Most athletes already consume more than RDA in habitual diet • Little evidence to support benefit of supplementation if eating a varied diet with complete/complementary protein • No risk until >40% of energy intake Calculation • Protein intake to ↑ muscle protein by 5kg.yr-1 in 80kg athlete • Muscle 75% water, 25% protein (i.e. 1.25kg ↑) • 1250/80kg/365d = 0.04g/kg/BM/d • 0.04 x 80kg = 3.2g protein/d ~100ml skim milk (assumes all protein enters the muscle) • If assume only 25% enters the muscle • Then 400ml skim milk Refs • Tipton, K., and R. Wolfe (2004) Protein and amino acids for athletes. Journal Sports Sci. 22: 65-79 • Meeusen and Watson (2007) Amino acids and the brain: Do they play a role in ‘central fatigue’? Int J Sports Nutr Ex Metab 17 • IJSNEM Volume 17 - 2007