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==What is Taurine?==

==What is Taurine?==

[[File:Feline taurine.jpg|300px|right]]

[[File:Feline taurine.jpg|300px|right|thumb|© Diffomédia/Masure]]

[[File:Taurine.jpg|300px|right|thumb|Role of taurine in the cat]]

[[File:Taurine.jpg|300px|right|thumb|Role of taurine in the cat]]

Taurine (2-aminoethanesulfonic acid) is a '''naturally occurring sulphonic acid produced in the [[Liver - Anatomy & Physiology|liver]]''' as an end product of [[Methionine and Cysteine - Nutrition|cysteine]] metabolism. Taurine is not incorporated into proteins but found free in animal tissues; the highest concentrations are found in brain, heart, and skeletal muscle. Although commonly referred to as an amino acid it lacks a carboxyl group and is not classified as a true amino acid. '''Dogs can synthesise taurine from dietary precursors''' and are typically able produce amounts sufficient to meet daily needs. '''Cats are unable to produce adequate amounts of taurine to meet requirements and pre-formed taurine is required in the diet.'''

Taurine (2-aminoethanesulfonic acid) is a '''naturally occurring sulphonic acid produced in the [[Liver - Anatomy & Physiology|liver]]''' as an end product of [[Methionine and Cysteine - Nutrition|cysteine]] metabolism. Taurine is not incorporated into proteins but found free in animal tissues; the highest concentrations are found in [[:Category:Nervous System - Anatomy & Physiology|brain]], [[Heart - Anatomy & Physiology|heart]], and skeletal [[Muscles - Anatomy & Physiology|muscle]]. Although commonly referred to as an amino acid it lacks a carboxyl group and is not classified as a true amino acid. '''Dogs can synthesise taurine from dietary precursors''' and are typically able produce amounts sufficient to meet daily needs. '''Cats are unable to produce adequate amounts of taurine to meet requirements and pre-formed taurine is required in the diet.'''

==Why is it Important?==

==Why is it Important?==

==Roles in the Body==

==Roles in the Body==

'''Taurine is used in the conjugation of bile acids into bile salts in both dogs and cats'''. Cats only use taurine to form bile salts while dogs are able to conjugate [[Bile acids|bile acids]] to either taurine or glycine depending on availability of either amino acid<ref>Rabin J, et al. Dietary influences on bile acid conjugation in the cat. J Nutr 1976;106:1241-1246.</ref><ref>Wildgrube HJ, et al. Naturally occurring conjugated bile acids, measured by high-performance liquid chromatography, in human, dog, and rabbit bile. J Chrom. 1986;353:207-13.</ref>. Cats are unable to switch conjugation to glycine like dogs and other species and have an obligate loss of taurine in faeces. Bile salts are deconjugated in the intestinal lumen by bacteria and the deconjugated bile acids return to the liver via enterohepatic circulation. Taurine is then either absorbed by enterocytes, excreted in faeces, or further utilized by intestinal bacteria.  

'''Taurine is used in the conjugation of [[Bile acids|bile acids]] into bile salts in both dogs and cats'''. Cats only use taurine to form bile salts while dogs are able to conjugate bile acids to either taurine or glycine depending on availability of either amino acid<ref>Rabin J, et al. Dietary influences on bile acid conjugation in the cat. J Nutr 1976;106:1241-1246.</ref><ref>Wildgrube HJ, et al. Naturally occurring conjugated bile acids, measured by high-performance liquid chromatography, in human, dog, and rabbit bile. J Chrom. 1986;353:207-13.</ref>. Cats are unable to switch conjugation to glycine like dogs and other species and have an obligate loss of taurine in faeces. Bile salts are deconjugated in the intestinal lumen by bacteria and the deconjugated bile acids return to the liver via enterohepatic circulation. Taurine is then either absorbed by enterocytes, excreted in faeces, or further utilized by intestinal bacteria. <br>

Taurine also plays a role in normal retinal and myocardial function, osmoregulation, platelet aggregation, modulation of calcium flux within cells, reproduction, and immune response.  

Taurine also plays a role in normal retinal and myocardial function, osmoregulation, platelet aggregation, modulation of calcium flux within cells, reproduction, and immune response.  

==Consequences of Taurine Deficiency==

==Consequences of Taurine Deficiency==

[[Image:174223 Right4.jpg|right|200px|thumb|There is an area of tapetal hyperreflectivity surrounded by hyporeflectivity in the lateral tapetal fundus located at the area centralis.]]

[[Image:174223 Right4.jpg|right|300px|thumb|There is an area of tapetal hyperreflectivity surrounded by hyporeflectivity in the lateral tapetal fundus located at the area centralis.]]

[[File:Taurine-deficient cat.jpg|right|200px|thumb|A 2D echocardiography image of taurine deficiency related dilated cardiomyopathy.]]

[[File:Taurine-deficient cat.jpg|right|300px|thumb|A 2D echocardiography image of taurine deficiency related dilated cardiomyopathy.]]

[[File:Kitty barty LVtxt.jpg|right|200px|thumb|An M-mode echocardiography image from the same cat as above.]]

[[File:Kitty barty LVtxt.jpg|right|300px|thumb|An M-mode echocardiography image from the same cat as above.]]

===Dog:===  

===Dog:===  

Taurine-deficient DCM has been reported in dogs<ref name="Fascetti">Fascetti AJ, et al. Taurine deficiency in dogs with dilated cardiomyopathy: 12 cases (1997-2001). JAVMA 2003;223:1137-1141.</ref><ref name="Belanger">Belanger MC, et al. Taurine-deficient dilated cardiomyopathy in a family of golden retrievers. JAAHA 2005;41:284-91.</ref><ref name="Kittleson">Kittleson MD, et al. Results of the multicenter spaniel trial (MUST): taurine- and carnitine-responsive dilated cardiomyopathy in American cocker spaniels with decreased plasma taurine concentration. JVIM 1997;11:204-211.</ref><ref name="Backus">Backus RC, et al. Low Plasma Taurine Concentration in Newfoundland Dogs is Associated with Low Plasma Methionine and Cyst(e)ine Concentrations and Low Taurine Synthesis. J Nutr 2006;136:2525-2533.</ref>. This can occur despite being fed commercial diets labelled as complete and balanced when the diet provides inadequate supply of sulphur amino acids without additional taurine supplementation; contains poorly digestibly proteins<ref name="Torres">Torres CL, et al. Taurine status in normal dogs fed a commercial diet associated with taurine deficiency and dilated cardiomyopathy. JAPAN(Berl) 2003;87:359-72.</ref>; contains a higher fibre content that promotes a high faecal losses of bile salts<ref>Delaney SJ, et al. Plasma and whole blood taurine in normal dogs of varying size fed commercially prepared food. JAPAN(Berl) 2003 Jun;87(5-6):236-44.</ref>; or is fed to a large breed dog with a low capacity for synthesis of taurine<ref name="Backus"/><ref>Ko KS, et al. Differences in taurine synthesis rate among dogs relate to differences in their maintenance energy requirement J Nutr 2007;137:1171–1175.</ref>. Regardless of cause, taurine supplementation in these dogs appears to reverse some of the changes in cardiac function<ref name="Fascetti"/><ref name="Belanger"/><ref name="Kittleson"/>. Taurine supplementation is recommended for all dogs presenting with DCM until taurine deficiency has been ruled out.  

Taurine-deficient DCM has been reported in dogs<ref name="Fascetti">Fascetti AJ, et al. Taurine deficiency in dogs with dilated cardiomyopathy: 12 cases (1997-2001). JAVMA 2003;223:1137-1141.</ref><ref name="Belanger">Belanger MC, et al. Taurine-deficient dilated cardiomyopathy in a family of golden retrievers. JAAHA 2005;41:284-91.</ref><ref name="Kittleson">Kittleson MD, et al. Results of the multicenter spaniel trial (MUST): taurine- and carnitine-responsive dilated cardiomyopathy in American cocker spaniels with decreased plasma taurine concentration. JVIM 1997;11:204-211.</ref><ref name="Backus">Backus RC, et al. Low Plasma Taurine Concentration in Newfoundland Dogs is Associated with Low Plasma Methionine and Cyst(e)ine Concentrations and Low Taurine Synthesis. J Nutr 2006;136:2525-2533.</ref>. This can occur despite being fed commercial diets labelled as complete and balanced when the diet provides inadequate supply of sulphur amino acids without additional taurine supplementation; contains poorly digestibly proteins<ref name="Torres">Torres CL, et al. Taurine status in normal dogs fed a commercial diet associated with taurine deficiency and dilated cardiomyopathy. JAPAN(Berl) 2003;87:359-72.</ref>; contains a higher fibre content that promotes a high faecal losses of bile salts<ref>Delaney SJ, et al. Plasma and whole blood taurine in normal dogs of varying size fed commercially prepared food. JAPAN(Berl) 2003 Jun;87(5-6):236-44.</ref>; or is fed to a large breed dog with a low capacity for synthesis of taurine<ref name="Backus"/><ref>Ko KS, et al. Differences in taurine synthesis rate among dogs relate to differences in their maintenance energy requirement J Nutr 2007;137:1171–1175.</ref>. Regardless of cause, taurine supplementation in these dogs appears to reverse some of the changes in cardiac function<ref name="Fascetti"/><ref name="Belanger"/><ref name="Kittleson"/>. Taurine supplementation is recommended for all dogs presenting with DCM until taurine deficiency has been ruled out.  

====Recognised Syndromes Related to Taurine Deficiency====

====Recognised Syndromes Related to Taurine Deficiency====

#'''Dilated Cardiomyopathy''': The most well described consequence of taurine deficiency in dogs is the development of DCM<ref name="Fascetti"/><ref name="Belanger"/><ref name="Kittleson"/><ref name="Backus"/>. In this condition dogs develop right-sided cardiac failure with exercise intolerance, ascites and in some cases severe cardiac output failure. This condition may respond to cardiac support and taurine supplementation. Recommended doses include 500-1000 mg taurine orally three times a day. Cases of DCM not related to taurine deficiency may not respond to supplementation.

#'''Dilated Cardiomyopathy''': The most well described consequence of taurine deficiency in dogs is the development of DCM<ref name="Fascetti"/><ref name="Belanger"/><ref name="Kittleson"/><ref name="Backus"/>. In this condition dogs develop [[Heart Failure, Right-Sided|right-sided cardiac failure]] with exercise intolerance, ascites and in some cases severe cardiac output failure. This condition may respond to cardiac support and taurine supplementation. Recommended doses include 500-1000 mg taurine orally three times a day. Cases of DCM not related to taurine deficiency may not respond to supplementation.

#'''Retinal Lesions''': Blindness related to taurine deficiency is not common in dogs, but there are reports of dogs with low plasma taurine concentrations described to have hyper-reflective retinal lesions, similar to Feline Central Retinal Degeneration (FCRD) in cats<ref>PD, et al. The effectiveness of taurine and levocarnitine in dogs with heart disease. Vet Clin N Amer Sm Anim Prac 1998;28:1495-514. </ref>. This syndrome is not as well characterised as it has been in cats and little information regarding prognosis and response to treatment is available.  

#'''Retinal Lesions''': Blindness related to taurine deficiency is not common in dogs, but there are reports of dogs with low plasma taurine concentrations described to have hyper-reflective retinal lesions, similar to Feline Central Retinal Degeneration (FCRD) in cats<ref>PD, et al. The effectiveness of taurine and levocarnitine in dogs with heart disease. Vet Clin N Amer Sm Anim Prac 1998;28:1495-514. </ref>. This syndrome is not as well characterised as it has been in cats and little information regarding prognosis and response to treatment is available.

===Cat:===  

===Cat:===  

'''Taurine is an essential nutrient in cats due to''':  

'''Taurine is an essential nutrient in cats due to''':  

#Reduced activity of hepatic cysteine dioxygenase and cysteine sulphinate decarboxylase activity (two key enzymes in the conversion of cysteine to taurine) as compared with other species<ref>De la Rosa J et al. Metabolism of cysteine and cyteinesulfinate in rat and cat hepatocytes. J Nutr 1987;117:549-558.</ref> and #An obligate loss of taurine in bile acid conjugation. Clinical signs of taurine deficiency may develop in a matter of weeks to months of feeding a deficient diet.  

#Reduced activity of hepatic cysteine dioxygenase and cysteine sulphinate decarboxylase activity (two key enzymes in the conversion of cysteine to taurine) as compared with other species<ref>De la Rosa J et al. Metabolism of cysteine and cyteinesulfinate in rat and cat hepatocytes. J Nutr 1987;117:549-558.</ref> and  

#An obligate loss of taurine in bile acid conjugation. Clinical signs of taurine deficiency may develop in a matter of weeks to months of feeding a deficient diet.  

====Recognised Syndromes Related to Taurine Deficiency====  

====Recognised Syndromes Related to Taurine Deficiency====  

#'''Feline Central Retinal Degeneration (FCRD)''':  Taurine deficient cats develop hyper-reflective lesions in the area centralis of the [[Eye - Anatomy & Physiology#The Wall (retina, uvea and sclera)|retina]], which progresses to complete photoreceptor degeneration and ultimately blindness<ref>Anderson PA, et al. Biochemical lesions associated with taurine deficiency in the cat.  J Anim Sci 1979;49:1227-1234.</ref>. This condition is not reversible, but is very rare in cats fed diets with adequate taurine content.

#'''Feline Central Retinal Degeneration (FCRD)''':  Taurine deficient cats develop hyper-reflective lesions in the area centralis of the [[Eye - Anatomy & Physiology#The Wall (retina, uvea and sclera)|retina]], which progresses to complete photoreceptor degeneration and ultimately blindness<ref>Anderson PA, et al. Biochemical lesions associated with taurine deficiency in the cat.  J Anim Sci 1979;49:1227-1234.</ref>. This condition is not reversible, but is very rare in cats fed diets with adequate taurine content.

#'''[[Dilated Cardiomyopathy - Feline Cardiomyopathies|Dilated Cardiomyopathy]]''': Taurine deficiency in now an uncommon cause of DCM in cats as commercial diets are supplements with adequate taurine levels. Cats with taurine-deficient DCM may present with subclinical disease or in overt heart failure. Echocardiography usually demonstrates left atrium enlargement, dilation of both ventricles (see image), and decreased left ventricular contractility<ref>Pion PD, et al. Myocardial failure in cats associated with low plasma taurine: a reversible cardiomyopathy. Science 1987;237:764-768.</ref>. Supplementation with oral taurine (250 - 500 mg orally twice a day) may improve clinical signs in 1-3 weeks.  

#'''[[Dilated Cardiomyopathy - Feline Cardiomyopathies|Dilated Cardiomyopathy]]''': Taurine deficiency in now an uncommon cause of DCM in cats as commercial diets are supplements with adequate taurine levels. Cats with taurine-deficient DCM may present with subclinical disease or in overt heart failure. Echocardiography usually demonstrates left atrium enlargement, dilation of both ventricles (see image), and decreased left ventricular contractility<ref>Pion PD, et al. Myocardial failure in cats associated with low plasma taurine: a reversible cardiomyopathy. Science 1987;237:764-768.</ref>. Supplementation with oral taurine (250 - 500 mg orally twice a day) may improve clinical signs in 1-3 weeks.  

#'''Decreased Immune Response''': Prolonged taurine deficiency in cats can result in a range of abnormalities in the immune system, including leukopenia, neutrophil dyfunction depletion of cells from B-cell areas of lymph nodes and spleen<ref>Schuller-Levis G, et al. Immunologic consequences of taurine deficiency in cats. J Leukoc Biol 1990;47:321-331.</ref>. The clinical significance of immune dysfunction related to taurine deficiency is not well described.  

#'''Decreased Immune Response''': Prolonged taurine deficiency in cats can result in a range of abnormalities in the [[:Category:Immunology|immune system]], including leukopenia, neutrophil dyfunction depletion of cells from B-cell areas of [[ Lymph Nodes - Anatomy & Physiology|lymph nodes]] and [[Spleen - Anatomy & Physiology|spleen]]<ref>Schuller-Levis G, et al. Immunologic consequences of taurine deficiency in cats. J Leukoc Biol 1990;47:321-331.</ref>. The clinical significance of immune dysfunction related to taurine deficiency is not well described.  

#'''Poor Reproductive Performance''': Although taurine-deficient cats come into [[Oestrous Cycle - Cat|oestrus]] normally dietary taurine deprivation adversely affects feline pregnancy<ref name="Sturman">Sturman JA. Dietary taurine and feline reproduction and development. J Nutr 1991;121:S166-S170.</ref> it is associated with:

#'''Poor Reproductive Performance''': Although taurine-deficient cats come into [[Oestrous Cycle - Cat|oestrus]] normally dietary taurine deprivation adversely affects feline pregnancy<ref name="Sturman">Sturman JA. Dietary taurine and feline reproduction and development. J Nutr 1991;121:S166-S170.</ref> it is associated with:

:*abortion,  

:*abortion,  

:*poor kitten survival.  

:*poor kitten survival.  

::Taurine deficiency in queens has also been associated with congenital defects in kittens such as [[hydrocephalus]] and anencephaly, cerebellar dysgenesis, abnormal hind-limb development and thoracic kyphosis<ref>Sturman JA, et al. Feline maternal taurine deficiency: Effect on mother and offspring. J Nutr 1986;116:655-667.</ref><ref>Sturman JA and Lu P. Role of feline maternal taurine nutrition in fetal cerebellar development: and immunohistochemical study. Amino Acids 1997;13:369-377.</ref>. Taurine-deprived, live-born kittens have a poor postnatal survival rate, maturational delay, and reduced growth rates<ref name="Sturman"/>. Surviving kittens are often small and weak and are prone to various complications.   

::Taurine deficiency in queens has also been associated with congenital defects in kittens such as [[hydrocephalus]] and anencephaly, cerebellar dysgenesis, abnormal hind-limb development and thoracic kyphosis<ref>Sturman JA, et al. Feline maternal taurine deficiency: Effect on mother and offspring. J Nutr 1986;116:655-667.</ref><ref>Sturman JA and Lu P. Role of feline maternal taurine nutrition in fetal cerebellar development: and immunohistochemical study. Amino Acids 1997;13:369-377.</ref>. Taurine-deprived, live-born kittens have a poor postnatal survival rate, maturational delay, and reduced growth rates<ref name="Sturman"/>. Surviving kittens are often small and weak and are prone to various complications.   

:5.  '''[[Ear - Anatomy & Physiology#Deafness|Deafness]]''': Taurine deficiency has been associated with delayed auditory brainstem- evoked response maturation in cats resulting in hearing loss<ref>Vallecalle-Sandoval MH, et al. Comparison of the developmental changes of the brainstem auditory evoked response (BAER) in taurine-supplemented and taurine-deficient kittens. Int J Dev Neurosci 1991;9(6):571-9.</ref>.

:5.  '''[[Ear - Anatomy & Physiology#Deafness|Deafness]]''': Taurine deficiency has been associated with delayed auditory brainstem-evoked response maturation in cats resulting in hearing loss<ref>Vallecalle-Sandoval MH, et al. Comparison of the developmental changes of the brainstem auditory evoked response (BAER) in taurine-supplemented and taurine-deficient kittens. Int J Dev Neurosci 1991;9(6):571-9.</ref>.

==Toxicity==

==Toxicity==

==References==

==References==

<references/>

<references/>

[[Category:Amino Acids]]

[[Category:Amino Acids]]