Protein Lecture Presentation PDF

Protein Dr Joel Craddock [email protected]...

Protein Dr Joel Craddock [email protected] 1 1 Icebreaker: What factors impact your selection of protein sources? Is protein quality and/or timing a consideration when planning and cooking meals? Is daily energy intake a consideration? Why or why not? 2 2 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 1  Lecture Objectives By the end of this lecture, you should be able to: Describe amino acids and how the structure of a protein affects its functions. Describe the digestion, absorption, and transportation of amino acids. Explain protein metabolism and the processes associated with skeletal muscle protein synthesis and breakdown. Determine daily protein recommendations for athletes and the amount, quality, distribution, and timing of protein intake before, during, and after exercise. Describe the effects of low protein and energy intakes on training, recovery, performance, and health. Translate protein recommendations into daily food intake, and assess an athlete’s dietary protein intake. Describe current protein intake guidelines for athletes and sedentary populations, and current and emerging literature to support or disputes these guidelines. Identify additional factors that interact with muscle protein metabolism, including energy balance, dietary protein source, quantity and timing, the presence of other macro and micro nutrients and age, 3 3 Structure and Function of Protein 4 4 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 2  The Basic Structure of an Amino Acid 5 5 Summary of the 20 Amino Acids Figure Amino acid number Classification Glucogenic Ketogenic Miscellaneous Alanine (Ala) 2 Dispensable Yes No Can be produced in the muscle from pyruvate but must be transported to the liver for conversion to pyruvate to produce glucose; an important glucose-generating pathway during Starvation Arginine (Arg) 14 Conditionally Yes No indispensable Asparagine (Asn) 12 Dispensable Yes No Aspartic acid (Asp) 10 Dispensable Yes No One of the two amino acids that make up the structure of the artificial sweetener aspartame Cysteine (Cys) 8 Conditionally Yes No indispensable Glutamic acid (Glu) 11 Dispensable Yes No Glutamine (Gln) 13 Conditionally Yes No Represents about half of all the amino acids in the amino indispensable acid pool; potent stimulator of the immune system and major source of fuel for immune cells Glycine (Gly) 1 Conditionally Yes No indispensable Histidine (His) 16 Indispensable Yes No Isoleucine (Ile) 5 Indispensable Yes Yes Branched chain amino acid; muscle can use as an energy source during prolonged endurance exercise when muscle glycogen stores are low 6 6 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 3  Summary of the 20 Amino Acids Figure Amino acid number Classification Glucogenic Ketogenic Miscellaneous Leucine (Leu) 4 Indispensable No Yes Branched chain amino acid; muscle can use as an energy source during prolonged endurance exercise when muscle glycogen stores are low; activates key signaling proteins necessary for skeletal muscle protein synthesis Lysine (Lys) 15 Indispensable No Yes Methionine 9 Indispensable Yes No (Met) Phenylalanine 17 Indispensable Yes Yes One of the two amino acids that make up the structure of the artificial sweetener (Phe) aspartame Proline (Pro) 20 Conditionally Yes No Indispensable Serine (Ser) 6 Dispensable Yes No Threonine (Thr) 7 Indispensable Yes Yes Tryptophan 19 Indispensable Yes Yes (Trp) Tyrosine (Tyr) 18 Conditionally Yes Yes Indispensable Valine (Val) 3 Indispensable Yes No Branched chain amino acid; muscle can use as an energy source during prolonged endurance exercise when muscle glycogen stores are low 7 7 Summary of the 20 Amino Acids 8 8 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 4  Protein Structure Determines Function Peptide Dipeptide, tripeptide Polypeptide Structure Primary Secondary Tertiary Quaternary 9 9 Protein Structure Primary structure − Structure of protein determined by amino acids (chemical bonds) Secondary structure − Determined by weak electrical attraction within polypeptides (H bonding > a-helix or b sheets) − Provides strength and rigidity Tertiary structure − Polypeptide chain twists and folds; side groups attracted = intricate shape (e.g. disulphide bridges in insulin) Quaternary structure − Interactions between multiple polypeptides (e.g. haemoglobin) 10 10 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 5  Protein Structure 11 11 Protein Structure 12 12 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 6  Functions of Proteins Protein category Functions Component of enzymes Enzymes are specialized proteins that speed up (catalyze) chemical reactions in cells Component of hormones Hormones, many of which are protein based, regulate metabolic processes; signaling proteins (cytokines) and signaling proteins are known as growth factors and can bind to the surface of a cell and influence its cellular processes; some amino acids stimulate signaling proteins necessary for skeletal muscle protein synthesis (MPS) Structural proteins Component of muscle, connective tissue, skin, hair, and nails Transport proteins Part of molecules that allow compounds to be transported, such as oxygen, carbon dioxide, iron, and fats Immune system proteins Fundamental component of the immune system Acid-base regulator Amino acids have both acid and basic groups, which help the body to achieve acid-base balance and optimal pH Fluid regulator Proteins, especially those found in the blood, help to maintain fluid balance Source of energy Under normal conditions, a minor energy source; under temporary stressful conditions, a small but important source of energy; under severe or prolonged stress, such as starvation, a major source of energy but to the detriment of health 13 13 Digestion, Absorption, and Transportation of Protein 14 14 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 7  Digestion and Absorption of Dietary Protein 15 15 Digestion and Absorption of Dietary Protein Commercially available protein supplements May be ‘predigested’ or hydrolysed. Could control “fast” or “slow” release 16 16 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 8  Amino Acid Pool and Turnover Free amino acids circulating in blood or fluid near cells Some of the amino acids have recently been absorbed from the gastrointestinal tract Most come from the breakdown of body tissues, including skeletal muscle tissue Average of 150 g of amino acids; ~80 g is glutamine More dispensable than indispensable amino acids Always in flux because of protein turnover 17 17 Amino Acid Pool and Turnover 18 18 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 9  Metabolism of Proteins and Amino Acids 19 19 Deamination 20 20 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 10  Skeletal Muscle Protein Turnover 21 21 Amino Acids Used for ATP Production 22 22 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 11  Protein Metabolism during Endurance Exercise – Glucose-alanine Cycle 23 23 Nitrogen Balance and Net Protein Balance Nitrogen balance − Difference between total nitrogen intake (protein) and total nitrogen losses (via urine and feces) Net protein balance − Difference between MPS and MPB − Achieved if MPS = MPB Positive nitrogen balance Growth period, for example, pregnancy Hypertrophy Negative nitrogen balance 24 24 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 12  Muscle anatomy and protein types Sarcoplasmic proteins Mitochrondrial proteins Myofibrillar proteins 25 25 Combined effect of exercise and protein 26 26 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 13  Combined effect of exercise and protein Phillips (2014). Sports Med 44 Supp 1 27 27 Protein Recommendations for Athletes 28 28 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 14  Protein Recommendations for Athletes a Exercising 4-5 times per week for 30 min, at < 55% VO2peak b Exercising 4-5 times per week for 45-60 min. Clinical Sports Nutrition (4th ed.) 2010. 29 29 Protein Recommendation Considerations Modern sports nutrition guidelines now consider several factors when recommending protein intake for athletes: The amount of protein per day The amount of protein at any one eating occasion The distribution of protein intake across meals and snacks over the day The food source/type of protein consumed The influence of the type, volume and timing of exercise in relation to protein needs The influence and interaction of other nutrients on protein metabolism The influence of energy balance and/or energy availability The body composition and performance goals of the athlete 30 30 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 15  Protein dose in a single eating occasion Young participants performed leg extension exercises, with a one-off dose of egg albumin protein post exercise. Protein dose varied between 0, 10, 20 and 40g protein per serve. Protein synthesis in the 4 hours following exercise was maximally stimulated at 20g, with no further increase after doubling protein intake. FSR = Fractional Synthesis Rate Moore DR et al. (2009) 31 31 Protein Dose and the Leucine Trigger Leucine has a unique signalling role in triggering the increase in muscle protein synthesis An exact leucine "threshold" for muscle protein synthesis has not been quantified from research Appears to be approx. 2-3g but many variables 32 32 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 16  Isolated vs compound/whole body resistance exercise 33 Macnaughton LS. et al. (2016). 33 Protein Intake for MPS and Age Older adults (71 ± 1 yrs) The plateau in muscle protein synthesis with increasing protein intake occurred at around 0.40 ± 0.19 g/kg in older men. Younger adults (22 ± 4 yrs) The plateau in muscle protein synthesis with increasing protein intake occurred at around 0.24 ± 0.06 g/kg in younger men. Moore DR. et al. (2015). 34 34 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 17  Protein Timing and Distribution Areta et al study compared three different patterns of ingestion of 80 g of protein during 12 h recovery after resistance exercise and the associated anabolic response in human skeletal muscle. Protein was ingested in 10, 20 or 40 g feedings using a pulsed, intermediate or bolus ingestion regimen respectively. 35 35 Protein Timing and Distribution Results indicate that repeated ingestion of 20 g of protein was superior for stimulating muscle protein synthesis during the 12 h experimental period. This study shows that the distribution of protein intake is an important variable to promote attainment and maintenance of peak muscle mass. 36 36 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 18  Protein Recommendations for Athletes 37 37 ©2019 Cengage Learning. All Rights Reserved. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part. 19