Protein and Amino Acid MetabolismProtein and Amino Acid Metabolism

Introduction - (FYI)Introduction - (FYI)

Energy plus buildingMade up of amino

acidsFuel source

Alanine, leucine, glutamine

Intro - StructureIntro - Structure

Nonessential (12)Essential (9)Peptide (-NH3)

Peptide bondsLarge number of

different structuresMost proteins contain

up to 300 amino acids

Intro - Animal versus PlantIntro - Animal versus Plant

Animal protein is complete and more protein per gram

Plant protein is incomplete and less protein per gram

For example: 2 ounces of fish = 14 g of protein 2 ounces of macaroni = 2 grams 2 ounces of beans = 5 grams Soy: the only complete plant source

Intro - How Much Protein?Intro - How Much Protein?

Minimum = 0.57 grams per kilogram of body weight

RDA for egg whites = 0.34 g/kgRDA = 0.8 g/kgRDA = 0.36 grams per pound10 percent of total caloric intake

Intro- Proteins in the dietIntro- Proteins in the diet

Most of digestion occurs in the small intestine/gut

Absorption into bloodJoins the amino acid

pool•Functions of proteins

•Structure•Transport•Enzymes•Hormones•Immune•Acid-base•Fluid balance•Energy•Movement

Amino Acid PoolAmino Acid Pool

Figure 8-3Blood, liver and skeletal muscleEquilibrium with bloodMovement of amino acids from one site to another

is very rapidLow or inadequate amino acids in one site can be

compensated with amino acids from another site.Constant catabolismHalf life of amino acids is a few days to a few

months.

Amino Acid PoolAmino Acid Pool

Nitrogen BalanceNitrogen Balance

An term used to indicate the balance in amino acids that are added to the body to those that are removed.

Positive balance indicates more amino acids are staying in the body than are being removed. e.g. muscle hypertrophy.

Negative balance indicates more amino acids are being removed than added. e.g. muscle atrophy.

Fasting/Atrophy Hypertrophy

Nitrogen BalanceNitrogen Balance

Protein RequirementsProtein Requirements

Nitrogen balance can be maintained with 0.57 g / kg of protein intake

Allowing for some error, the RDA for protein is set at 0.8 g/kg

A positive nitrogen balance depends on having both adequate protein and energy (calories) in the diet.

What is the best energy source for protein synthesis? Protein? Fat? Carbohydrate?

TransaminationTransamination

Figure 8-5, 8-6 and Equations 8-2, 8-3.

Transferring nitrogen from one amino acid to another

Examples Alanine + α

ketogluterate → glutamate + pyruvate

Aspartate + α ketogluterate → glutamate + oxaloacetate

Protein MetabolismProtein Metabolism

Protein provides only 5-10% of energy requirements during exercise.

1. Krebs cycle substrates2. Gluconeogenesis via the glucose-

alanine cycle3. Muscle hypertrophy (branch chain

amino acids)

Amino acid carbon skeletonsAmino acid carbon skeletonsFigure 8-7Krebs cycle is imperfectAmino acids provide missing elements

Glucose-Alanine CycleGlucose-Alanine Cycle

?

Ammonia (NH4)Ammonia (NH4)

Released during exerciseAccumulation of ammonia may contribute

to fatigue and ultimately become toxicα-ketogluterate + ammonia → glutamate +

another ammonia → glutamineGlutamine can be converted to glucose by

the kidneys when the ammonia is removed

Amino Acids and Muscle GrowthAmino Acids and Muscle Growth

Branch Chain Amino Acids: Leucine, Isoleucine, and Valine

Located mainly in skeletal muscle Nitrogen used for protein synthesis Carbons used for energy

20% of amino acids released from skeletal muscle are BBAA

However, skeletal muscle contains all amino acids

What does this mean in regard to protein supplements? Are certain amino acids more beneficial than others?

Speculation on Other Amino Acids (FYI)Speculation on Other Amino Acids (FYI)

Arginine, Lysine and Ornithine – hGHTrypophan – increase serotonin (decrease

pain perception)BCAA – block typrophan and serotonin

production (delay fatigue)Glutamine – remove ammoniaAspartates – enhance fat metabolismGlycine – formation of creatine

Do athletes need more protein?Do athletes need more protein?

Maybe. Resistance training

1.2-2.0 g per kg per day 15% of total calories

Endurance training 1.2-1.4 g per kg per day

How much protein are they already consuming?

NUTRITIONAL SUPPLEMENTS FOR WEIGHT GAIN SSE#68- Volume 11 (1998), Number 1 Priscilla M. Clarkson, Ph.D.

Arginine, ornithine, histidine, lysine, methionine, and phenylalanine are purported to have anabolic effects. Two studies reported that ingestion of arginine and ornithine in conjunction with strength training significantly increased body mass and decreased body fat compared to a placebo (Elam, 1988; Elam et al., 1989). However, body composition was only estimated from skinfold measures, and diet was not controlled.

It is claimed that these amino acids stimulate a release of growth hormone and insulin, and thereby increase muscle mass (Jacobson, 1990; Kreider et al., 1993).

Manufacturer-recommended doses of amino acid supplements are not likely to increase growth hormone and alter body weight. Commercially available supplements contain less than 4 g per serving; higher levels of amino acids can cause mild-to-severe stomach cramps and diarrhea. These supplements are costly, and the consequences of using selected amino acids for a long period of time have not been determined. High amounts of one amino acid may affect the body's absorption of other amino acids. There is little reason at this time to believe that amino-acid supplements will promote gains in muscle mass.

Do athletes need certain amino acids more than others?Do athletes need certain amino acids more than others?PROTEIN: POWER OR PUFFERY?

Jeffrey J. Zachwieja, PhDSenior Scientist, Gatorade Sports Science Institute

Digestion of dietary protein yields amino acids, which, after being absorbed, are available for metabolism and the growth and repair of all tissues in the body.

Because many athletes are purposefully trying to add more muscle, most believe the protein content of the diet should be considerably higher than that of non-athletes.

It is true that on average, athletes require slightly more protein (1.2-1.5 g/kg body weight; 0.5-0.7 grams/lb) than do less-active people (0.8-1.0 g/kg body weight; 0.4-0.5 grams/lb).

However, it is far from true that in order to meet this additional need, athletes must rely upon protein and amino acid supplements.

Further, there is simply no scientific evidence to support the idea that the protein or amino acids in supplements are more effective for athletes than protein in ordinary foods.

Do athletes need more protein during recovery from exercise?Do athletes need more protein during recovery from exercise?

Exercise is catabolic.Protein is needed for muscle repair,

etc

DIETARY PROTEIN, AMINO ACID SUPPLEMENTS, AND RECOVERY DIETARY PROTEIN, AMINO ACID SUPPLEMENTS, AND RECOVERY FROM EXERCISEFROM EXERCISE

Martin J. Gibala, Ph.D. GSSI

DIETARY PROTEIN, AMINO ACID SUPPLEMENTS, AND RECOVERY DIETARY PROTEIN, AMINO ACID SUPPLEMENTS, AND RECOVERY FROM EXERCISEFROM EXERCISE

Martin J. Gibala, Ph.D. GSSI

The maximum daily protein requirement for endurance- or resistance-trained athletes is 1.2-1.7 g per kg body weight (0.55-0.77 g/lb). This requirement can easily be met through diet alone—without the use of supplements—provided that sound nutrition principles are followed and energy intake is sufficient to maintain body weight.

Amino acids are always a minor source of fuel, usually accounting for less than 5% of total energy expenditure. If enough carbohydrate is ingested, i.e., ~1.2 g·kg-1·h-1 (0.55 g·lb-1·h-1) in 15-30 min intervals during the first

2-5 h of recovery, protein supplementation does not further increase muscle glycogen replenishment. However, if no food or too little carbohydrate is consumed, ingestion of protein or specific amino acids during recovery from prolonged exercise may accelerate glycogen resynthesis.

Ingesting a single drink containing ~0.1 g/kg of essential amino acids during the first few hours of recovery from heavy resistance exercise will produce a transient, net positive increase in muscle protein balance. It is uncertain if ingesting amino acids immediately before exercise or ingesting carbohydrate along with amino acids, either immediately before exercise or during recovery, further enhances the rate of muscle protein buildup during recovery.

Ingesting several doses of essential amino acids during recovery will promote a net "anabolic" environment over 24 h, but it remains to be determined if the acute effects of supplementation eventually lead to greater gains in muscle mass following habitual training.

Postexercise protein intake enhances whole-body and leg protein accretion in humans

DEANNA K. LEVENHAGEN; CHRISTOPHER CARR; MICHAEL G. CARLSON; DAVID J. MARON; MYFANWY J. BOREL; PAUL J. FLAKOLL

Departments of Surgery, Biochemistry and Medicine, Vanderbilt University Medical Center, Nashville, TN

MEDICINE & SCIENCE IN SPORTS & EXERCISE 2002;34:828-837

ABSTRACT LEVENHAGEN, D. K., C. CARR, M. G. CARLSON, D. J. MARON, M. J. BOREL, and P. J. FLAKOLL. Postexercise protein intake enhances whole-body and leg protein accretion in humans. Med. Sci. Sports Exerc., Vol. 34, No. 5, pp. 828-837, 2002.

Purpose: Exercise increases the use of amino acids for glucose production and stimulates the oxidation of amino acids and other substrates to provide ATP for muscular contraction, and thus the availability of amino acids and energy for postexercise muscle protein synthesis may be limiting. The purpose of this study was to determine the potential of postexercise nutrient intake to enhance the recovery of whole-body and skeletal muscle protein homeostasis in humans.

Methods: Primed-continuous infusions of L-[1-13C]leucine and L-[ring-2H5]phenylalanine were initiated in the antecubital vein and blood was sampled from a femoral vein and a heated (arterialized) hand vein. Each study consisted of a 30-min basal, a 60-min exercise (bicycle at 60% O2max), and a 180-min recovery period. Five men and five women were studied three times with an oral supplement administered immediately following exercise in random order: NO = 0, 0, 0; SUPP = 0, 8, 3; or SUPP+PRO = 10, 8, 3 g of protein, carbohydrate, and lipid, respectively.

Results: Compared to NO, SUPP did not alter leg or whole-body protein homeostasis during the recovery period. In contrast, SUPP+PRO increased plasma essential amino acids 33%, leg fractional extraction of phenylalanine 4-fold, leg uptake of glucose 3.5-fold, and leg and whole-body protein synthesis 6-fold and 15%, respectively. Whereas postexercise intake of either NO or SUPP resulted in a net leg release of essential amino acids and net loss of whole-body and leg protein, SUPP+PRO resulted in a net leg uptake of essential amino acids and net whole-body and leg protein gain.

Conclusions: These findings suggest that the availability of amino acids is more important than the availability of energy for postexercise repair and synthesis of muscle proteins.

Macronutrient intake and whole body protein metabolism following resistance exercise

Brian D. ROY; Jonathon R. FOWLES; Robert HILL; MARK A. TARNOPOLSKYDepartments of Kinesiology, Pathology, and Medicine, McMaster University, Hamilton, Ontario,

MEDICINE & SCIENCE IN SPORTS & EXERCISE 2000;32:1412-1418ROY, B. D., J. R. FOWLES, R. HILL, and M A. TARNOPOLSKY. Macronutrient intake and whole body protein metabolism following resistance exercise. Med. Sci. Sports Exerc., Vol. 32, No. 8, pp. 1412-1418, 2000.

The provision of carbohydrate (CHO) supplements following resistance exercise attenuated muscle protein (PRO) degradation (Roy et al. J. Appl. Physiol. 82:1882-1888, 1997). The addition of PRO may have a synergistic effect upon whole body protein balance by increasing synthesis (Biolo et al. Am. J. Physiol. 273:E122-E129, 1997).

Purpose: To determine if the macronutrient composition of a postexercise beverage would alter muscle anabolism and/or catabolism following resistance exercise.

Methods: We provided isoenergetic CHO (1 g·kg-1) and CHO/PRO/FAT supplements and placebo (PL) immediately (t = 0 h) and 1 h (t = +1 h) following resistance exercise (9 exercises/3 sets/80% 1 RM) to 10 young, healthy, resistance-trained males. Whole body leucine turnover was determined from L-[1-13C]leucine kinetics at 4 h postexercise.

Results: No differences were observed for urinary 3-methylhistidine or urea nitrogen excretion between the trials. Leucine flux was significantly elevated at 4 h postexercise for both CHO/PRO/FAT (177.59 ± 12.68 mol·kg -1·h-1) and CHO (156.18 ± 7.77 mol·kg-1·h-1) versus PL (126.32 ± 10.51 mol·kg-1·h-1) (P < 0.01). Whole body leucine oxidation was elevated at 4 h for CHO/PRO/FAT (29.50 ± 3.34 mol·kg-1·h-1) versus CHO (16.32 ± 2.33 mol·kg-1·h-1) (P < 0.01) and PL (21.29 ± 2.54 mol·kg-1·h-1) (P < 0.05). Nonoxidative leucine disposal (NOLD) was significantly elevated at 4 h for both CHO/PRO/FAT (148.09 ± 10.37 mol·kg-1·h-1) and CHO (139.86 ± 7.02 mol·kg-1·h-1) versus PL (105.03 ± 8.97 mol·kg-

1·h-1) (P < 0.01).

Conclusions: These results suggest that consumption of either CHO or CHO/PRO/FAT immediately and 1 h following a resistance training bout increased NOLD as compared with a placebo.

Anabolic Processes During RecoveryAnabolic Processes During Recovery

Protein during post-exercise may aid in muscle recovery/repair.

Carbohydrate alone may be just as effective.If helpful, only 0.1 g/kg of protein every 1-2

hours is needed.The type of protein seems to not influence

protein synthesisGood sources are milk, tuna, peanut butter,

etc.

Key TopicsKey Topics

Protein intake Amino acid pool Transamination

Function of proteins related to exercise