Carnosine is naturally produced by the body in the liver[2] from beta-alanine and histidine. Like carnitine, carnosine is composed of the root word carn, meaning "flesh", alluding to its prevalence in meat.[3] There are no plant-based sources of carnosine.[4] Carnosine is readily available as a synthetic nutritional supplement.
Carnosine is synthesized within the body from beta-alanine and histidine. Beta-alanine is a product of pyrimidine catabolism[5] and histidine is an essential amino acid. Since beta-alanine is the limiting substrate, supplementing just beta-alanine effectively increases the intramuscular concentration of carnosine.[6][7]
Carnosine has a pKa value of 6.83, making it a good buffer for the pH range of animal muscles.[8] Since beta-alanine is not incorporated into proteins, carnosine can be stored at relatively high concentrations (millimolar). Occurring at 17–25 mmol/kg (dry muscle),[9] carnosine (β-alanyl-L-histidine) is an important intramuscular buffer, constituting 10-20% of the total buffering capacity in type I and II muscle fibres.
Carnosine has been shown to scavenge reactive oxygen species (ROS) as well as alpha-beta unsaturated aldehydes formed from peroxidation of cell membrane fatty acids during oxidative stress. It also buffers pH in muscle cells, and acts as a neurotransmitter in the brain. It is also a zwitterion, a neutral molecule with a positive and negative end.[citation needed]
Carnosine is considered as a geroprotector.[14] Carnosine can increase the Hayflick limit in human fibroblasts,[15] as well as appearing to reduce the telomere shortening rate.[16] Carnosine may also slow aging through its anti-glycating properties (chronic glycolyating is speculated to accelerate aging).[17]
Carnosine can chelatedivalent metal ions.[11][18] It has been suggested that binding Ca2+ may displace protons, thereby providing a link between Ca2+ and H+ buffering. [19] However, there is still controversy as to how much Ca2+ is bound to carnosine under physiological conditions. [20]
Research has demonstrated a positive association between muscle tissue carnosine concentration and exercise performance.[21][22][23] β-Alanine supplementation is thought to increase exercise performance by promoting carnosine production in muscle. Exercise has conversely been found to increase muscle carnosine concentrations, and muscle carnosine content is higher in athletes engaging in anaerobic exercise.[21]
^Alan R. Hipkiss (2009). "Chapter 3: Carnosine and Its Possible Roles in Nutrition and Health". Advances in Food and Nutrition Research.
^"beta-ureidopropionate + H2O => beta-alanine + NH4+ + CO2". reactome. Archived from the original on 2013-10-23. Retrieved 2020-02-08. Cytosolic 3-ureidopropionase catalyzes the reaction of 3-ureidopropionate and water to form beta-alanine, CO2, and NH3 (van Kuilenberg et al. 2004).
^Derave W, Ozdemir MS, Harris R, Pottier A, Reyngoudt H, Koppo K, Wise JA, Achten E (August 9, 2007). "Beta-alanine supplementation augments muscle carnosine content and attenuates fatigue during repeated isokinetic contraction bouts in trained sprinters". J Appl Physiol. 103 (5): 1736–43. doi:10.1152/japplphysiol.00397.2007. PMID17690198. S2CID6990201.
^Hill CA, Harris RC, Kim HJ, Harris BD, Sale C, Boobis LH, Kim CK, Wise JA (2007). "Influence of beta-alanine supplementation on skeletal muscle carnosine concentrations and high intensity cycling capacity". Amino Acids. 32 (2): 225–33. doi:10.1007/s00726-006-0364-4. PMID16868650. S2CID23988054.
^ abReddy, V. P.; Garrett, MR; Perry, G; Smith, MA (2005). "Carnosine: A Versatile Antioxidant and Antiglycating Agent". Science of Aging Knowledge Environment. 2005 (18): pe12. doi:10.1126/sageke.2005.18.pe12. PMID15872311.
^Rashid, Imran; Van Reyk, David M.; Davies, Michael J. (2007). "Carnosine and its constituents inhibit glycation of low-density lipoproteins that promotes foam cell formation in vitro". FEBS Letters. 581 (5): 1067–70. doi:10.1016/j.febslet.2007.01.082. PMID17316626. S2CID46535145.
^Boldyrev, A. A.; Stvolinsky, S. L.; Fedorova, T. N.; Suslina, Z. A. (2010). "Carnosine as a natural antioxidant and geroprotector: From molecular mechanisms to clinical trials". Rejuvenation Research. 13 (2–3): 156–8. doi:10.1089/rej.2009.0923. PMID20017611.
^McFarland, G; Holliday, R (1994). "Retardation of the Senescence of Cultured Human Diploid Fibroblasts by Carnosine". Experimental Cell Research. 212 (2): 167–75. doi:10.1006/excr.1994.1132. PMID8187813.
^Shao, Lan; Li, Qing-Huan; Tan, Zheng (2004). "L-Carnosine reduces telomere damage and shortening rate in cultured normal fibroblasts". Biochemical and Biophysical Research Communications. 324 (2): 931–6. doi:10.1016/j.bbrc.2004.09.136. PMID15474517.
