The Science of Muscle Growth and Repair By William Cabot M.D., FAAOS

Transcription

1 The Science of Muscle Growth and Repair By William Cabot M.D., FAAOS Part 2 - The Role Individual Amino Acids Play in Muscle growth and Repair American Casein Company has been a worldwide leader in supplying protein powders for over fifty years. Protein products are composed of individual amino acids that are the magical substances critical to repair or build muscle. The role that amino acids play far exceeds just building muscle. It is the individual amino acids that our protein products are composed of that are the magical substances critical to repair or build muscle. The role that amino acids play far exceeds just building muscle. Amino acids are integral in the production of enzymes, hormones, blood components, and maintenance of our acid base balance. They are essential to maintain the body in homeostasis and play an integral role in almost all physiological processes that keep us alive (1). Growth of bodily tissues such as muscles, tendons, bone, and organs, from the cellular level up requires an adequate supply of protein. Our skeletal system is largely composed of a protein substance called collagen which contributes to ligaments, tendons, muscles, skin, teeth, and nails (2). Proteins are made of long and short polypeptide chains which are in turn composed of amino acids linked together. Some food and nutritional products function better when the polypeptide chains are shorter (some peptide chains have 2-20 amino acids) and this is the rationale for supplying hydrolyzed protein products. Hydrolysis breaks up the longer polypeptide chains into shorter chains of amino acids. Building or repairing muscle requires hormones made from amino acids such as insulin and growth hormone. The neurotransmitters that regulate hormone synthesis which in turn regulates

2 the growth of muscles are composed of amino acids. Proteins that transport the nutrients for muscle synthesis and the enzymes required to facilitate the processes of muscle growth and repair all have amino acids as a base. In this article we will describe many of the individual amino acids which play an active role in muscle growth and repair of the musculoskeletal system. Some body builders are so intent and focused on the significance of the individual acids that they skew their protein intake to incorporate certain acids more than others (3). There are a total of 20 amino acids. Eleven of these are called non-essential because the body can produce them in the liver. The other 9 are essential amino acids because we must get them from the food and supplements we eat. This makes them more critical. A complete protein source is one that contains all the essential and non-essential amino acids. Casein, whey, and soy are all complete protein sources. What follows is a description of amino acids important in musculoskeletal healing. Others not described also have important roles, but space does not permit us to delve into all of them. You may note a D or an L in front of the name of an individual amino acid. The amino acids typically come in two forms: a D- form and an L- form. They are called stereoisomers and are chemically mirror images of each other. The amino acids typically found in bodily proteins are L- form.

3 Lysine is probably best known for the help it provides to persons who suffer with cold sores. It has a direct role in collagen formation. Lysine It increases calcium absorption, thus helping to prevent osteoporosis (10). It helps convert fatty acids to energy which translates into a person s increased ability to exercise to build muscle. Glutamine is a non-essential amino acid that is present in very large amounts. With regard to musculoskeletal healing it plays a major part in the synthesis of proteins, DNA, RNA, collagen, components of cartilage, and even other amino acids (9). Glutamine It has a role in prevention of our immune system being suppressed, generally enhances protein stimulation, and has been linked to survival after major stress events such as surgery, trauma, burns, and infection (4). During these episodes it plays a role in enhancement of protein synthesis and prevents or reduces catabolism or breakdown of our bodily protein structures (12).

4 This amino acid plays a significant role in tissue healing. It is frequently mentioned in conjunction with carnosine which is another chemical form of histidine. Histidine Strenuous workout sessions typically produce tiny tears in the muscle and this is followed by an inflammatory and then a healing phase. It is during that healing phase that we see muscle growth via repair. Deficiencies of histidine are associated with impairment of the healing process and impairment of connective tissue regeneration (11). In 1998 the Nobel Prize was awarded to scientists who discovered that arginine was the key to the chemical cascade which results in Nitric Oxide causing increased blood flow. This not only had vast effects for male sexual difficulties but more blood flow brings the nutrients where we need them during exercise and faster recovery after exercise. Arginine Arginine stimulates release of both growth hormone and insulin and plays a role in many facets of cell growth itself by being a precursor for nucleic acid synthesis. One study revealed that a controlled group of patients supplemented with arginine lived longer (13). Arginine serves as a precursor for both collagen and creatine synthesis. Creatine is a high energy phosphate compound located in muscles and nerves. Glycine It is a significant component of collagen from which connective tissues arise. It plays a role in the release of growth hormone which is integral in the healing process (14).

5 Methionine and Cysteine These two amino acids serve as sources of sulfur, which is a basic component of connective tissues. Studies on wound healing in animals revealed that those who were protein deficient were able to be corrected by the administration of these two substances (15). Proline Collagen, which is the major component of connective tissues, is comprised of almost one third proline residues. This amino acid plays a part in amelioration of pain. Phenylalanine Our brains make endorphins and enkephalins which are natural opioid like substances with a role in pain suppression. D-Phenylalaniine has the ability to inhibit enzymes that degrade enkephalin and thus increase our pain tolerance (16). Summary Protein intake and its subsequent digestion into amino acids are major factors in the processes of healing and growth. Casein, whey, soy protein isolate, and milk protein concentrates are all excellent sources of these building blocks for protein synthesis.

6 References 1. The Benefits of Protein; Feb 2013; Cabot W.; 2. Guyton, Arthur C., Textbook of Medical Physiology, ninth ed., International Journal of Sport Nutrition. 1993;3: Failure of commercial oral amino acid supplements to increase serum growth hormone concentrations in male body builders; Lambert M, et al. 4. Nutrition Applied To Injury rehabilitation and Sports Medicine; CRC Press, 1995, ; Bucci L. 5. J Nutr Feb 2006vol 136 no Neutraceutical Effects of Branched Chain Amino Acid on Skeletal Muscle, Yoshiharu S et al. 6. Acta Endocrinol (Copenh) 1979 Mar;90(3); The influence of amino acids and somatostatin on prolactin and growth hormone release in man. Bratush-Marrain P, et al. 7. J Clin Endocrinol Metabolism 1965 Aug;25: Plasma growth hormone response to intravenous administration of amino acids. Knopf RF, et al. 8. Young sub Kwon and Kravitz, How do muscles grow; Nutr Rev 1990 Aug;48(8); Is glutamine a conditionally essential amino acid?; Lacey JM, et al. 10. Nutrition 1992 Nov-Dec;8(6); Dietary l-lysine and calcum metabolism in humans. Civitelli R., et al. 11. Surgery 1982 Jan;91(1): Carnosine, histidine, and wound healing. Fitzpatrick DW et al. 12. JPEN J Parenteral Enteral Nutr 1990 July-Aug; 14(4 suppl):40s-44s. Glutamine metabolism and its physiologic importance. Smith RJ. 13. Am J Clin Nutr February 2001 vol 73 no 2: ; Effect of perioperative nutrition on nutritional status, immune function, postoperative morbidity, and survival in severely malnourished head and neck cancer patients: Marian AE van Bkhorst-van-der Flier, et al. 14. Acta Endocrinol(Copenh) 1980 Mar;93(3); Glycine Stimulated Growth Hormone Release in Man. Kasai K, et al. 15. J. Bio. Chem., 212,705, 1955; The incorporation of sulphur amino acids into proteins of regenerating wound healing. Williamson MD, et al.

7 16. Adv Pain Res Ther. 1983;5: Use of D-phenylalanine, an enkephalinase inhibitor, in the treatment of intractable pain.. Budd K