Information AboutCreatine |
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Creatine is Nitrogen ous Organic Acid that naturally occurs in Vertebrate s and helps to supply energy to Muscle and nerve cells. Creatine was identified in 1832 when Michel Eugène Chevreul discovered it as a component of Skeletal Muscle which he later named creatine after the Greek word for flesh, ''Kreas''. FUNCTION Creatine (by way of conversion to and from Phospho-Creatine) is present and functions in all vertebrates, as well as some invertebrates, in conjunction with the enzyme Creatine Kinase. A similar system based on arginine/phosphoarginine operates in many Invertebrates via the action of Arginine Kinase (for review see Ellington et al. 2001) The presence of this energy buffer systems keeps the ATP / ADP ratio high at subcellular places where ATP is needed, which ensures that the free energy of ATP remains high and minimizes the loss of adenosine nucleotides, which would cause cellular dysfunction. Such high-energy phosphate buffers in the form of Phosph-Creatine or Phospho-Arginine are known as Phosphagen s. In addition, due to the presence of subcompartmentalized Creatine Kinase Isoforms at specific sites of the cell, the Phospho-Creatine/Creatine Kinase system also acts as an intracellular energy transport system from those places where ATP is generated (mitochondria and glycolysis) to those places where energy is needed and utilized, e.g. at the the myofibrils for muscle contraction, at the sarcoplasmic reticulum (SR) for calcium pumping and many more biological processes that depend on ATP (for review see Wallimann et al. 1992). Ellington WR. Evolution and physiological roles of phosphagen systems. Annu Rev Physiol. 2001;63:289-325. Review. Wallimann T, Wyss M, Brdiczka D, Nicolay K, Eppenberger HM. Intracellular compartmentation, structure and function of creatine kinase isoenzymes in tissues with high and fluctuating energy demands: the 'phosphocreatine circuit' for cellular energy homeostasis. Biochem J. 1992 Jan 1;281 ( Pt 1):21-40. Review. BIOSYNTHESIS In the human body, approximately half of the daily creatine is biosynthesized mainly in the vertebrates by the use of parts from three different Amino Acid s - Arginine , Glycine , and Methionine . The rest is taken in by alimentary sources mainly from fresh fish and meat. 95% of it is later stored in the skeletal muscles, with the rest in the Brain , Heart , Testes , Inner Ear Hair Cells (Shin et al. 2007) and other organs and cells (Hemmer and Wallimann 1994; Wallimann et al. 1992; 2007). Refs: Shin JB, Streijger F, Beynon A, Peters T, Gadzala L, McMillen D, Bystrom C, Van der Zee CE, Wallimann T, Gillespie PG. Hair Bundles Are Specialized for ATP Delivery via Creatine Kinase. Neuron. 2007 Feb 1;53(3):371-86. T. Wallimann, M. Wyss, D. Brdiczka, K. Nicolay, and H.M. Eppenberger. Intracellular compartmentation, structure and function of creatine kinase isoenzymes: the "phospho-creatine circuit" for cellular energy homeostasis. Biochem. J. 281: 21-40 (1992). (Comprehensive review with the PCr-circuit model) T. Wallimann, and W. Hemmer. Creatine kinase in non-muscle tissues and cells. Mol. Cell Biochem. 133/134: 193-220 (1994) ; Met - The amidinotransferase (AGAT), EC 2.1.4.1], is a Mitochondrial Enzyme responsible for catalyzing the first rate-limiting step of creatine biosynthesis, and is primarily expressed in the Kidneys . The second enzyme in the pathway (GAMT, guanidinoacetate N-methyltransferase, EC:2.1.1.2) is primarily expressed in the liver. Genetic deficiencies in the creatine biosynthetic pathway lead to various severe neurological defects. SOURCES In humans, approximately half of stored creatine originates from food (mainly from fresh Meat and Fish ). Since vegetables do not contain creatine, vegetarians clearly show lower levels of muscle creatine that rise upon creatine supplementation more than those of non-vegetarians.Burke DG, Chilibeck PD, Parise G, Candow DG, Mahoney D, Tarnopolsky M. Effect of creatine and weight training on muscle creatine and performance in vegetarians. Med Sci Sports Exerc. 2003 Nov;35(11):1946-55 CREATINE AND THE TREATMENT OF MUSCULAR DISEASES Creatine supplementation has been, and continues to be, investigated as a possible therapeutic approach for the treatment of muscular, neurological and neuromuscular diseases ( Arthritis , Congestive Heart Failure , disuse atrophy, gyrate atrophy, McArdle's Disease , Huntington's Disease , miscellaneous neuromuscular diseases, Mitochondrial Disease s, Muscular Dystrophy , Neuroprotection , etc.). Two scientific studies have indicated that creatine may be beneficial for neuromuscular disorders. First, a study (Klivenyi et al. 1999) by MDA-funded researcher M. Flint Beal of Cornell University Medical Center demonstrated that creatine was twice as effective as the prescription drug Riluzole in extending the lives of mice with the degenerative neural disease Amyotrophic Lateral Sclerosis (ALS, or Lou Gehrig's disease). Beal suspects that the neuroprotective effects of creatine in the mouse model of ALS are due either to an increased availability of energy to injured nerve cells or to a blocking of the chemical pathway that leads to Cell Death . Second, a study by Canadian researchers Mark Tarnopolsky and Joan Martin of McMaster University Medical Centre in Hamilton, Ontario found that creatine can cause modest increases in strength in people with a variety of neuromuscular disorders. The latter paper was published in the March 1999 issue of '' Neurology ''. SEE ALSO
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