Carnitine

Structural formula
Structural formula of the L isomer of carnitine
General
Surname	Carnitine
other names	Trimethyl hydroxybutyrobetaine (3-carboxy-2-hydroxypropyl) - N , N , N -trimethylammoniumhydroxid
Molecular formula	C 7 H 15 NO 3
Brief description	colorless, crystalline powder
External identifiers / databases
CAS number 406-76-8 EC number 206-976-6 ECHA InfoCard 100.006.343 PubChem 288 Wikidata Q243309
Drug information
ATC code	A16 AA01
properties
Molar mass	161.20 g mol −1
Physical state	firmly
Melting point	190–195 ° C (decomposition)
solubility	very soluble in water: 800 g l −1 (20 ° C)
safety instructions
Please note the exemption from the labeling requirement for drugs, medical devices, cosmetics, food and animal feed GHS labeling of hazardous substances Caution H and P phrases H: 315-319-335 P: 261-305 + 351 + 338
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Carnitine is a chemical compound that occurs in two isomeric forms. One of them, L - Carnitine ( INN : Levocarnitine ), is produced in living beings from the amino acids lysine and methionine and plays an essential role in the energy metabolism in the transport of fatty acids between the cytosol and the cell organelles such as the mitochondria .

Stereoisomerism

Carnitine is chiral because it contains a stereocenter. There are thus two enantiomers , the ( R ) -form [(-) - L- carnitine] and the ( S ) -form [(+) - D- carnitine]. The D- carnitine is of practically no importance; when carnitine is mentioned without a descriptor , L- carnitine is always meant.

Isomers of carnitine
Surname	L- carnitine	D- carnitine
other names	( R ) -Carnitine (-) - Carnitine Levocarnitine	( S ) -Carnitine (+) - carnitine
Structural formula
CAS number	541-15-1	541-14-0
	406-76-8 ( DL )
EC number	208-768-0	625-884-0
	206-976-6 ( DL )
ECHA info card	100.007.972	100.154.337
	100.006.343 ( DL )
PubChem	10917	2724480
	288 ( DL )
DrugBank	DB00583	-
	- ( DL )
Wikidata	Q20735709	Q27108687
	Q243309 ( DL )

properties

L- Carnitine reacts with fatty acids in the metabolism, which creates activated fatty acids . Carnitine has performed this function in interaction with coenzyme A from. Fatty acids can only be transported through the mitochondrial membrane when bound to L- carnitine. Fatty acids are fed to the β-oxidation via the carnitine acyltransferase system .

In the intestine of carnitine by the intestinal flora first trimethylamine and consecutive trimethylamine oxide formed. The human body can produce L- carnitine from the amino acids methionine and lysine itself, but it is mainly obtained from meat .

Occurrence

L- carnitine is found in large quantities in red meat, especially sheep and lamb. Poultry, on the other hand, has little carnitine content, while vegetarian foods contain little or no L- carnitine. With a mixed diet, between 100 and 300 mg of L- carnitine are consumed daily , in contrast to ovo-lacto-vegetarians who only consume 15-25% of this amount, while the proportion with a vegan diet is around 3–10% lies. The remaining requirement is covered by the endogenous synthesis, if the essential cofactors vitamin C , vitamin B ₆ , niacin and iron are available in sufficient quantities. The bioavailability of L- carnitine from food is 54 to 87%. The absorption depends strongly on the carnitine content of the food, but also on its composition.

The total amount of L- carnitine in the body is around 20-25 g, the proportion being particularly high in tissues with a high fatty acid metabolism. 98% of the reserves of carnitine are stored in the heart and skeletal muscles. About 20 mg is excreted in the urine every day via the kidneys. The normal level of L- carnitine in plasma is between 40 and 60 µmol / l, of which about 70-85% is available as free carnitine. The remainder is esterified with a fatty acid as acylcarnitine.

Since L- carnitine is water-soluble, it is removed from the blood of kidney patients during hemodialysis . This has the consequence that dialysis patients have very low blood L- carnitine levels. Patients with advanced renal failure often take L- carnitine, either orally or intravenously, to make up for these losses.

synthesis

L- carnitine can be obtained in various ways on an industrial scale. For example, via a biotechnological process that imitates the body's own biosynthesis : the precursor of L- carnitine (γ- butyrobetaine ) is converted into L- carnitine with the help of gram-negative bacteria ( rhizobia ) in large fermentation vessels.

use

Patients with systemic primary carnitine deficiency (SPCD) are given carnitine as a dietary supplement. Carnitine is also used as a fat burner .

Carnitine as a "fat burner"

The additional intake of carnitine is controversial in studies. Scientists from the Institute for Food Science and Ecotrophology at the University of Hanover concluded in 1994 that “L-carnitine does not have an independent property as a 'fat burner' or a 'slimming aid'.” The carnitine-dependent fatty acid transport occurs at maximum speed even at physiological carnitine concentrations. An increase in sales through additional carnitine doses can therefore be excluded. Human studies show that carnitine supplements lead to an increase in carnitine levels in the blood, but there is no evidence of a corresponding intracellular increase. The North Rhine-Westphalia consumer center expresses itself as follows about carnitine as a dietary supplement and alleged fat burner:

“The claim that the body has to break down 34 g of muscle to produce 1 g of carnitine is simply wrong, it uses protein building blocks from food for this. Additional carnitine intake in tablet form can neither increase the carnitine content in the muscle cells nor the speed of fat burning. Nor does it affect the body's fat percentage when dieting. (...) Superfluous carnitine is excreted with the urine. However, it cannot be ruled out that the body's own production of carnitine will cease with a long-term high intake. (...) Carnitine is just as ineffective as a slimming agent as it is as a performance enhancer, cardiac tonic, potency enhancer and anti-cancer agent. "

In 2016, a meta-analysis found limited effectiveness.

Carnitine in sports

Endurance athletes in particular often take L- carnitine as a dietary supplement , as some studies suggest that taking L- carnitine can improve performance. This increase in performance relates to the regeneration after great sporting exertion. Carnitine is traded as one of the most powerful fat burners in sport.

Carnitine in cancer

In a randomized double-blind study by the University of Greifswald, it was shown in 2012 that the daily intake of 4 g of L-carnitine in advanced pancreatic cancer could stop the dangerous weight loss ( cachexia ). While the weight in the control group decreased by an average of 1.4%, the weight in the carnitine group increased significantly by 3.4% . The median survival time also increased from 399 to 519 days and the length of stay in hospital decreased from 41 to 36 days (not significant). Carnitine is being studied to reduce muscle breakdown in cancer.

L -Carnitin content in food

L- Carnitine content in food in mg per 100 g of food

Food	L- carnitine mg / 100 g	Food	L- carnitine mg / 100 g	Food	L- carnitine mg / 100 g	Food	L- carnitine mg / 100 g
Meat extract	3686	calf	69.7-105	Mushrooms	1.3-15	Breast milk substitute	1-4.3
Roe deer , stag , elk , reindeer	35-193	wild boar	18-46	poultry	4.3-13.3	Cooking oil , butter , margarine	0-1.1
Sheep , goat	16.7-190	Meat products	1.2-38.6	sea ​​animals	1.7-13.2	Cereals (bread, pasta, rice)	0.33-0.75
Horse , kangaroo	117-166	Rabbits	10.2-24.4	cheese	0.6-12.7	nuts	0.02-0.67
Beef	45-143	Domestic pig	14.4-24	Milk , dairy products	2.1-9.7	vegetables	0.05-0.53
Hare	44.1-120	Wild birds	3-21.1	Broths	1.1-6.1	fruit	0.01-0.35

Carnitine as a hair restorer

L- Carnitine is marketed as a dietary supplement and in shampoos as an anti- hair loss agent . Apart from a small study from 2007 (19 male, 32 female subjects, age 21–60 years) with topically applied carnitine tartrate, there is no scientific basis for this. The authors ascribed the effect to a reduction in the formation of hair growth inhibiting factors.

history

Carnitine was first isolated in 1905 by Vladimir Gulewitsch and his colleague Robert Krimberg . They also prepared a platinum salt of carnitine and determined the molecular formula; Krimberg found the correct structural formula the following year. Carnitine is said to have been found around the same time by Friedrich Kutscher in Marburg, who called it Novain . His structural formula was wrong and Krimberg soon proved that both are identical. In 1952 it was identified by Gottfried Fraenkel with the insect growth factor vitamin that they had isolated . This immediately led to the discovery of its role in lipid metabolism and in the mitochondria. ${\displaystyle B_{T}}$

literature

• Heinz Löster: Carnitine and Cardiovascular Diseases. Ponte Press, Bochum 2003, ISBN 3-920328-45-0 .
• Heinz Löster: Carnitine and its importance in cardiovascular diseases. Ponte Press, Bochum 2007, ISBN 978-3-920328-50-8 .

Web links

• Scientific study on carnitine and lipid metabolism (PDF; 98 kB)
• Scientific study on the effect of L- carnitine on regeneration after exercise
• Hanne Seline Marie Gustavsen: Determination of the L-carnitine content in raw and prepared vegetable and animal foods . (PDF; 1.72 MB) PhD thesis

Individual evidence

1. ↑ ^{a b c} Carnitine data sheet (PDF) from Merck , accessed on January 19, 2011.
2. ↑ ^{a b} Data sheet L-Carnitine inner salt from Sigma-Aldrich , accessed on November 3, 2016 ( PDF ).
3. ^ Heinz Löster: Biochemical fundamentals of the effects of Carnitine. In: Carnitine and Cardiovascular Diseases. Ponte Press, Bochum 2003, ISBN 3-920328-45-0 , pp. 3-48.
4. ↑ Robert A Koeth, Zeneng Wang, Bruce S Levison, Jennifer A Buffa, Elin Org, Brendan T Sheehy, Earl B Britt, Xiaoming Fu, Yuping Wu, Lin Li, Jonathan D Smith, Joseph A DiDonato, Jun Chen, Hongzhe Li, Gary D Wu, James D Lewis, Manya Warrier, J Mark Brown, Ronald M Krauss, WH Wilson Tang, Frederic D Bushman, Aldons J Lusis, Stanley L Hazen: Intestinal microbiota metabolism of l-carnitine, a nutrient in red meat, promotes atherosclerosis. In: Nature Medicine. 19, 2013, p. 576, doi: 10.1038 / nm.3145 .
5. ↑ ^{a b} Hanne Seline Marie Gustavsen: Determination of the L-carnitine content in raw and prepared vegetable and animal foods. (PDF; 1.8 MB) Doctoral thesis at the Physiological Institute of the University of Veterinary Medicine Hannover, 2000.
6. ↑ ^{a b c} Axel G. Feller, Daniel Rudman: Role of carnitine in human nutrition. In: The Journal of Nutrition. Volume 118, Issue 5, pp. 541-547, January 1988 PMID 3284979 . jn.nutrition.org (PDF; 1.6 MB)
7. ↑ ^{a b} C. J. Rebouche, CA Chenard: Metabolic fate of dietary carnitine in human adults: identification and quantification of urinary and fecal metabolites. In: The Journal of Nutrition. Volume 121, Issue 4, pp. 539-546, April 1991 PMID 2007906 . jn.nutrition.org (PDF; 1.3 MB)
8. ↑ CJ Rebouche: Carnitine function and requirements during the life cycle. In: FASEB journal: official publication of the Federation of American Societies for Experimental Biology. Volume 6, Number 15, December 1992, pp. 3379-3386, PMID 1464372 .
9. ^ G. Guarnieri: Carnitine in maintenance hemodialysis patients. In: Journal of renal nutrition: the official journal of the Council on Renal Nutrition of the National Kidney Foundation. Volume 25, number 2, March 2015, pp. 169-175, doi: 10.1053 / j.jrn.2014.10.025 , PMID 25600394 .
10. ^ Axel Kleemann, Jürgen Engel, Bernd Kutscher, Dieter Reichert: Pharmaceutical Substances. 4th edition. 2 volumes. Thieme, Stuttgart 2000, ISBN 3-13-558404-6 (online with biannual additions and updates)
11. ↑ Pilar Magoulas L, W Ayman El-Hattab: Systemic primary carnitine deficiency: an overview of clinical manifestations, diagnosis, and management. In: Orphanet Journal of Rare Diseases. 7, 2012, p. 68, doi: 10.1186 / 1750-1172-7-68 .
12. ↑ Alexander Ströhle, Maike Wolters, Andreas Hahn: Nutrient Supplements and Functional Food for Weight Loss - Desire and Reality. In: Nutrition & Medicine. 19, 2004, pp. 121-128.
13. ↑ MD Vukovich, DL Costill, WJ Fink: Carnitine supplementation: effect on muscle carnitine and glycogen content during exercise. In: Med Sci Sports Exerc. 26, 1994, pp. 1122-1129.
14. ↑ ABC of slimming. Consumer advice center NRW, Düsseldorf 2004, ISBN 3-933705-91-6 .
15. ↑ M. Pooyandjoo, M. Nouhi, S. Shab-Bidar, K. Djafarian, A. Olyaeemanesh: The effect of (L-) carnitine on weight loss in adults: a systematic review and meta-analysis of randomized controlled trials. In: Obesity reviews: an official journal of the International Association for the Study of Obesity. Volume 17, number 10, October 2016, pp. 970-976, doi: 10.1111 / obr.12436 , PMID 27335245 .
16. ↑ M. Kraft u. a .: L-Carnitine-supplementation in advanced pancreatic cancer (CARPAN) - a randomized multicentre trial In: Nutrition Journal. 2012. PMID 22824168
17. ^ R. Ringseis, J. Keller, K. Eder: Mechanisms underlying the anti-wasting effect of L-carnitine supplementation under pathologic conditions: evidence from experimental and clinical studies. In: European Journal of Nutrition . Volume 52, number 5, August 2013, pp. 1421-1442, doi: 10.1007 / s00394-013-0511-0 , PMID 23508457 .
18. ↑ K. Foitzik et al .: Indications that topical L-carnitine-L-tartrate promotes human hair growth in vivo. J. Dermatol. Sci. 2007, 48 (2), 141.
19. ↑ K. Foitzik et al .: L-Carnitine-L-tartrate promotes human hair growth in vitro. Exp. Dermacol. 2007, 16, 936.
20. ↑ Gulevich, Krimberg: On the knowledge of the extractive substances of the muscles . In: Z. f. Physiol. Chemie , Volume 45, 1905, pp. 326-328
21. ↑ Anatoly Bezkorovainy: Carnosine, carnitine, and Vladimir Gulevich . In: J. Chem. Education , Vol. 51, 1974, pp. 652-654.
22. ↑ Bezkorovainy. In: J. Chem. Education , Volume 51, 1974, p. 653, he cites R. Krimberg. In: Z. f. Physiol. Chemie , Volume 49, 1906, p. 89, Volume 50, 1907, p. 361.
23. ^ F. Kutscher: To the knowledge of the Novain In: Z. Physiol. Chem. , Vol. 49, 1905, pp. 47-49, digitized
24. ↑ George Wolf: The Discovery of a Vitamin Role for Carnitine: the First 50 Years In: Journal of Nutrition , Volume 136, 2006, pp. 2131-2134, jn.nutrition.org

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