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Revision as of 18:14, 9 December 2010

For the use of creatine to enhance athletic performance, see Creatine supplements.
Not to be confused with creatinine.
Creatine
Structural formula of creatine
Structural formula of creatine
Spacefill model of creatine
Spacefill model of creatine
Names
Preferred IUPAC name
Creatine
Systematic IUPAC name
2-(1-Methylcarbamimidamido)acetic acid
Other names
Creatin

Kreatin
2-(Methylguanidino) ethanoic acid

(α-Methylguanido)acetic acid
Identifiers
3D model (JSmol)
3DMet
907175
ChEBI
ChemSpider
DrugBank
ECHA InfoCard 100.000.278 Edit this at Wikidata
EC Number
  • 200-306-6
240513
KEGG
MeSH Creatine
UNII
  • InChI=1S/C4H9N3O2/c1-7(4(5)6)2-3(8)9/h2H2,1H3,(H3,5,6)(H,8,9) checkY
    Key: CVSVTCORWBXHQV-UHFFFAOYSA-N checkY
  • InChI=1/C4H9N3O2/c1-7(4(5)6)2-3(8)9/h2H2,1H3,(H3,5,6)(H,8,9)
    Key: CVSVTCORWBXHQV-UHFFFAOYAV
  • CN(CC(O)=O)C(N)=N
  • [H]/N=C(\N)/N(C)CC(=O)O
Properties
C4H9N3O2
Molar mass 131.135 g·mol−1
Melting point 255 °C (491 °F; 528 K)
13.3 g dm-3 (at 18 °C)
log P -0.2
Acidity (pKa) 3.429
Basicity (pKb) 10.568
Isoelectric point 8.47
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
checkY verify (what is checkY☒N ?)

Creatine is a nitrogenous organic acid that occurs naturally in vertebrates and helps to supply energy to all cells in the body, primarily muscle, by increasing the formation of Adenosine triphosphate (ATP). 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 meat, κρέας (kreas). In solution, creatine is in equilibrium with creatinine.[1]

Biosynthesis

Creatine is naturally produced in the human body from amino acids primarily in the kidney and liver. It is transported in the blood for use by muscles. Approximately 95% of the human body's total creatine is located in skeletal muscle.[2]

Creatine is not an essential nutrient, as it is manufactured in the human body from L-arginine, glycine, and L-methionine.[3]

In humans and animals, approximately half of stored creatine originates from food (mainly from meat). Since vegetables do not contain creatine, vegetarians show lower levels of muscle creatine, but show the same levels after using supplements.[4]

The enzyme GATM (L-arginine:glycine 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 and pancreas.[5]

The second enzyme in the pathway (GAMT, guanidinoacetate N-methyltransferase, EC:2.1.1.2) is primarily expressed in the liver and pancreas.[5]

Genetic deficiencies in the creatine biosynthetic pathway lead to various severe neurological defects.[6]

The pathway for the synthesis of creatine
Arg - Arginine; GATM - Glycine amidinotransferase; GAMT - Guanidinoacetate N-methyltransferase; Gly - Glycine; Met - Methionine; SAH - S-adenosyl homocysteine; SAM - S-adenosyl methionine.
The color scheme is as follows:enzymes, coenzymes and the Met part, substrate names, the Gly part, the Arg part

Health effects

Use as food supplement

Main article: Creatine supplements

Creatine supplements are sometimes used by athletes, bodybuilders, and others who wish to gain muscle mass, typically consuming 2 to 3 times the amount that could be obtained from a very-high-protein diet. A survey of long-time use gives the creatine content of several foods.[7] The Mayo Clinic states that creatine has been associated with asthmatic symptoms and warns against consumption by persons with known allergies.[8]

While there was once some concern that creatine supplementation could affect hydration status and heat tolerance and lead to muscle cramping and diarrhea, recent studies have shown these concerns to be unfounded.[9][10]

There is less concern today than there used to be about possible kidney damage from creatine, although there are reports of kidney damage, such as interstitial nephritis; patients with kidney disease should avoid use of this supplement.[8] In similar manner, liver function may be altered, and caution is advised in those with underlying liver disease although studies have shown little or no adverse impact on kidney or liver function from oral creatine supplementation.[11]

In theory, creatine may alter the activities of insulin. Caution is advised in patients with diabetes or hypoglycemia, and in those taking drugs, herbs, or supplements that affect blood sugar. Serum glucose levels may need to be monitored by a health-care professional, and medication adjustments may be necessary.

Long-term administration of large quantities of creatine is reported to increase the production of formaldehyde, which has the potential to cause serious unwanted side-effects. However, this risk is largely theoretical because urinary excretion of formaldehyde, even under heavy creatine supplementation, does not exceed normal limits.[12]

Extensive research over the last decade has shown that oral creatine supplementation at a rate of 5 to 20 grams per day appears to be very safe and largely devoid of adverse side-effects [13] while at the same time, effectively improving the physiological response to resistance exercise, increasing the maximal force production of muscles in both men and women.[14][15]

Pharmacokinetics

Endogenous serum or plasma creatine concentrations in healthy adults are normally in a range of 2–12 mg/L. A single 5 g (5000 mg) oral dose in healthy adults results in a peak plasma creatine level of approximately 120 mg/L at 1–2 hours post-ingestion. Creatine has a fairly short elimination half-life, averaging just less than 3 hours, so to maintain an elevated plasma level it would be necessary to take small oral doses every 3–6 hours throughout the day. After the "loading dose" period (1–2 weeks, 12-24g a day), it is no longer necessary to maintain a consistently high serum level of Cr. As with most supplements, each person has their own genetic "preset" amount of creatine they can hold. The rest is eliminated out of the body as waste. Creatine is consumed by the body fairly quickly. And if one wishes to maintain the high concentration of Cr ,Post - loading dose, 2-5g daily is the standard amount to intake.[16][17][18]

Pregnancy and breastfeeding

Creatine cannot be recommended during pregnancy or breastfeeding due to a lack of scientific information. Pasteurized cow's milk contains higher levels of creatine than human milk.[19]

Treatment of diseases

Creatine has been demonstrated to cause modest increases in strength in people with a variety of neuromuscular disorders.[20] Creatine supplementation has been, and continues to be, investigated as a possible therapeutic approach for the treatment of muscular, neuromuscular, neurological and neurodegenerative diseases (arthritis, congestive heart failure, Parkinson's disease, disuse atrophy, gyrate atrophy, McArdle's disease, Huntington's disease, miscellaneous neuromuscular diseases, mitochondrial diseases, muscular dystrophy, and neuroprotection).[citation needed]

A study demonstrated that creatine is 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). The neuroprotective effects of creatine in the mouse model of ALS may be 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.[21] A similarly promising result has been obtained in prolonging the life of transgenic mice affected by Huntington's disease. Creatine treatment lessened brain atrophy and the formation of intranuclear inclusions, attenuated reductions in striatal N-acetylaspartate, and delayed the development of hyperglycemia.[22]

Cognitive ability

A placebo-controlled double-blind experiment found that vegetarians who took 5 grams of creatine per day for six weeks showed a significant improvement on two separate tests of fluid intelligence, Raven's Progressive Matrices, and the backward digit span test from the WAIS. The treatment group was able to repeat longer sequences of numbers from memory and had higher overall IQ scores than the control group. The researchers concluded that "supplementation with creatine significantly increased intelligence compared with placebo."[23] A subsequent study found that creatine supplements improved cognitive ability in the elderly.[24] A study on young adults (0.03 g/kg/day for six weeks, e.g., 2 g/day for 150-pound individual) failed, however, to find any improvements.[25]

See also

References

  1. ^ Cannan, R. K.; Shore, A. (1928). "The Creatine-Creatinine Equilibrium. The Apparent Dissociation Constants of Creatine and Creatinine" (PDF). Biochem. J. 22 (4): 920–29. PMC 1252207. PMID 16744118. Retrieved 29 October 2010.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  2. ^ "Creatine". MedLine Plus Supplements. U.S. National Library of Medicine. 20 July 2010. Retrieved 16 August 2010.
  3. ^ "Creatine". Beth Israel Deaconess Medical Center. Retrieved 23 August 2010.
  4. ^ Burke DG, Chilibeck PD, Parise G, Candow DG, Mahoney D, Tarnopolsky M (2003). "Effect of creatine and weight training on muscle creatine and performance in vegetarians". Medicine and science in sports and exercise. 35 (11): 1946–55. doi:10.1249/01.MSS.0000093614.17517.79. PMID 14600563.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  5. ^ a b "ETH ETH E-Collection: Methylglyoxal, creatine and mitochondrial micro-compartments - ETH E-Collection" (PDF). E-collection.ethbib.ethz.ch. 19 April 2008. doi:10.3929/ethz-a-004636659. Retrieved 16 August 2010. {{cite web}}: Check |doi= value (help)
  6. ^ "L-Arginine:Glycine Amidinotransferase". Ncbi.nlm.nih.gov. Retrieved 16 August 2010.
  7. ^ "Creatine: is it really safe for long-term use?". Pponline.co.uk. Retrieved 16 August 2010.
  8. ^ a b "Creatine: Safety". MayoClinic.com. Retrieved 16 August 2010.
  9. ^ Lopez RM, Casa DJ, McDermott BP, Ganio MS, Armstrong LE, Maresh CM (2009). "Does creatine supplementation hinder exercise heat tolerance or hydration status? A systematic review with meta-analyses". Journal of Athletic Training. 44 (2): 215–23. doi:10.4085/1062-6050-44.2.215. PMC 2657025. PMID 19295968.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  10. ^ Dalbo VJ, Roberts MD, Stout JR, Kerksick CM (2008). "Putting to rest the myth of creatine supplementation leading to muscle cramps and dehydration". British Journal of Sports Medicine. 42 (7): 567–73. doi:10.1136/bjsm.2007.042473. PMID 18184753. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  11. ^ Poortmans JR, Francaux M (2000). "Adverse effects of creatine supplementation: fact or fiction?". Sports Medicine. 30 (3): 155–70. doi:10.2165/00007256-200030030-00002. PMID 10999421. {{cite journal}}: Unknown parameter |month= ignored (help)
  12. ^ Francaux M, Poortmans JR (2006). "Side effects of creatine supplementation in athletes". International Journal of Sports Physiology and Performance. 1 (4): 311–23. PMID 19124889. {{cite journal}}: Unknown parameter |month= ignored (help)
  13. ^ Bizzarini E, De Angelis L (2004). "Is the use of oral creatine supplementation safe?". The Journal of Sports Medicine and Physical Fitness. 44 (4): 411–6. PMID 15758854. {{cite journal}}: Unknown parameter |month= ignored (help)
  14. ^ Bemben MG, Lamont HS (2005). "Creatine supplementation and exercise performance: recent findings". Sports Medicine. 35 (2): 107–25. PMID 15707376.
  15. ^ Kreider RB (2003). "Effects of creatine supplementation on performance and training adaptations" (PDF). Molecular and Cellular Biochemistry. 244 (1–2): 89–94. doi:10.1023/A:1022465203458. PMID 12701815. {{cite journal}}: Unknown parameter |month= ignored (help)
  16. ^ Kamber M, Koster M, Kreis R, Walker G, Boesch C, Hoppeler H. Creatine supplementation--part I: performance, clinical chemistry, and muscle volume. Med. Sci. Sports Exer. 31: 1763-1769, 1999.
  17. ^ Deldicque L, Décombaz J, Zbinden Foncea H, Vuichoud J, Poortmans JR, Francaux M. Kinetics of creatine ingested as a food ingredient. Eur. J. Appl. Physiol. 102: 133-143, 2008.
  18. ^ R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 8th edition, Biomedical Publications, Foster City, CA, 2008, pp. 366-368.
  19. ^ Hülsemann J, Manz F, Wember T, Schöch G (1987). "[Administration of creatine and creatinine with breast milk and infant milk preparations]". Klinische Pädiatrie (in German). 199 (4): 292–5. doi:10.1055/s-2008-1026805. PMID 3657037.{{cite journal}}: CS1 maint: multiple names: authors list (link)
  20. ^ Tarnopolsky M, Martin J (1999). "Creatine monohydrate increases strength in patients with neuromuscular disease". Neurology. 52 (4): 854–7. PMID 10078740. {{cite journal}}: Unknown parameter |month= ignored (help)
  21. ^ Klivenyi P, Ferrante RJ, Matthews RT; et al. (1999). "Neuroprotective effects of creatine in a transgenic animal model of amyotrophic lateral sclerosis". Nature Medicine. 5 (3): 347–50. doi:10.1038/6568. PMID 10086395. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  22. ^ Andreassen OA, Dedeoglu A, Ferrante RJ; et al. (2001). "Creatine increase survival and delays motor symptoms in a transgenic animal model of Huntington's disease". Neurobiology of Disease. 8 (3): 479–91. doi:10.1006/nbdi.2001.0406. PMID 11447996. {{cite journal}}: Explicit use of et al. in: |author= (help); Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  23. ^ Rae C, Digney AL, McEwan SR, Bates TC (2003). "Oral creatine monohydrate supplementation improves brain performance: a double-blind, placebo-controlled, cross-over trial". Proceedings. Biological Sciences / the Royal Society. 270 (1529): 2147–50. doi:10.1098/rspb.2003.2492. PMC 1691485. PMID 14561278. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  24. ^ McMorris T, Mielcarz G, Harris RC, Swain JP, Howard A (2007). "Creatine supplementation and cognitive performance in elderly individuals". Neuropsychology, Development, and Cognition. Section B, Aging, Neuropsychology and Cognition. 14 (5): 517–28. doi:10.1080/13825580600788100. PMID 17828627. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)
  25. ^ Rawson ES, Lieberman HR, Walsh TM, Zuber SM, Harhart JM, Matthews TC (2008). "Creatine supplementation does not improve cognitive function in young adults". Physiology & Behavior. 95 (1–2): 130–4. doi:10.1016/j.physbeh.2008.05.009. PMID 18579168. {{cite journal}}: Unknown parameter |month= ignored (help)CS1 maint: multiple names: authors list (link)

External links


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