Changes

==Roles in the Body==

==Roles in the Body==

Thiamin (as TPP) is responsible for the decarboxylation of α-ketoacids and acyl-CoA derivatives during amino acid and glucose metabolism. The TPP-dependant enzyme transketolase is also involved in metabolism of glucose and ribose synthesis via the pentose phosphate pathway.  

Thiamin (as TPP) is responsible for the decarboxylation of α-ketoacids and aceyl-CoA derivatives during amino acid and glucose metabolism. The TPP-dependant enzyme transketolase is also involved in metabolism of glucose and ribose synthesis via the pentose phosphate pathway.  

Thiamin is one of the [[Nutrition Glossary#Essential Nutrients|essential nutrients]] involved with the clinical sequelae of refeeding syndrome<ref>Mehanna HM, et al. Refeeding syndrome: what it is, and how to prevent and treat it. BMJ 2008;336:1495-1498.</ref>. Refeeding syndrome can occurs when chronically starved animals are given a large bolus of readily absorbed carbohydrates without adequate amount of rate-limiting essential nutrients, specifically thiamin, [[Potassium - Nutrition|potassium]], and [[Magnesium - Nutrition|magnesium]]. The intracellular shift of these nutrients can cause rapid and profound clinical signs, leading to death if untreated.

Thiamin is one of the [[Nutrition Glossary#Essential Nutrients|essential nutrients]] involved with the clinical sequelae of refeeding syndrome<ref>Mehanna HM, et al. Refeeding syndrome: what it is, and how to prevent and treat it. BMJ 2008;336:1495-1498.</ref>. Refeeding syndrome can occurs when chronically starved animals are given a large bolus of readily absorbed carbohydrates without adequate amount of rate-limiting essential nutrients, specifically thiamin, [[Potassium - Nutrition|potassium]], and [[Magnesium - Nutrition|magnesium]]. The intracellular shift of these nutrients can cause rapid and profound clinical signs, leading to death if untreated.

Puppies fed thiamin deficient diets experience '''slow growth, inappetance, weight loss, coprophagia, neurological abnormalities (circling, torticollis, ataxia, and central nervous system depression) and sudden death'''. Dogs with acute thiamin deficiency develop bilaterally symmetric grey matter necrosis; chronic deficiencies can progress to myocardial and peripheral nerve degeneration<ref name="NRC"/>.

Puppies fed thiamin deficient diets experience '''slow growth, inappetance, weight loss, coprophagia, neurological abnormalities (circling, torticollis, ataxia, and central nervous system depression) and sudden death'''. Dogs with acute thiamin deficiency develop bilaterally symmetric grey matter necrosis; chronic deficiencies can progress to myocardial and peripheral nerve degeneration<ref name="NRC"/>.

====Cats:====  

====Cats:====  

Cats fed thiamin deficient diet develop '''anorexia initially, followed by progressive clinical signs of neurological involvement in 1-2 weeks'''. The neurological signs include flexion of the head, impaired proprioception and righting reflexes, seizures, progressive weakness, and death<ref name="NRC"/>. Kittens fed thiamin deficient diets can also develop ataxia and mydriasis. Bilaterally symmetric grey matter necrosis is also a feature of thiamin deficiency in cats and kittens<ref>Moon S, et al. Clinical signs, MRI features, and outcomes of two cats with thiamine deficiency secondary to diet change. J Vet Sci 2013;14:499-502.</ref>.

Cats fed thiamin deficient diet develop '''anorexia initially, followed by progressive clinical signs of neurological involvement in 1-2 weeks'''. The neurological signs include flexion of the head, impaired proprioception and righting reflexes, seizures, progressive weakness, and death<ref name="NRC"/>. Kittens fed thiamin deficient diets can also develop ataxia and [[Eye - Anatomy & Physiology#Reflexes with Optic Nerve as the Sensory Arm|mydriasis]]. Bilaterally symmetric grey matter necrosis is also a feature of thiamin deficiency in cats and kittens<ref>Moon S, et al. Clinical signs, MRI features, and outcomes of two cats with thiamine deficiency secondary to diet change. J Vet Sci 2013;14:499-502.</ref>.<br>

Conditions associated with diuresis (e.g., chronic disease, such as renal disease or [[Diabetes Insipidus|diabetes]], or therapeutic intervention, such as intravenous fluids or increased water intake to manage [[Cystitis|lower urinary disease]]) can result in increased loss of thiamin and may increase daily requirements. Patients on chronic haemodialysis are also at an increased risk for developing a deficiency.  

Conditions associated with diuresis (e.g. chronic disease, such as [[:Category:Kidney - Pathology|renal disease]] or [[Diabetes Insipidus|diabetes]], or therapeutic intervention, such as [[Fluid therapy|intravenous fluids]] or increased water intake to manage [[Cystitis|lower urinary disease]]) can result in increased loss of thiamin and may increase daily requirements. Patients on chronic haemodialysis are also at an increased risk for developing a deficiency. <br>

Thiamin deficiencies can also occur due to low dietary intake, presence of compounds in food that directly antagonise thiamin, and vitamin degradation during cooking. Thiaminases are present in certain freshwater and marine fishes, but this enzyme is readily denatured with heating<ref name="NRC"/>. Additionally sulphite preservatives in meats can degrade thiamin resulting in clinical signs of deficiency<ref>Studdert VP and Labuc RH. Thiamin deficiency in cats and dogs associated with feeding meat preserved with sulphur dioxide. Aust Vet J 1991;68:54-57.</ref>. Thiamin is particularly sensitive to degradation with increased temperature especially under alkaline conditions, such as can occur during canned foods production. This higher rate of thiamin degradation requires commercial pet food manufacturers to monitor and supplement thiamin according to expected losses.  

Thiamin deficiencies can also occur due to low dietary intake, presence of compounds in food that directly antagonise thiamin, and vitamin degradation during cooking. Thiaminases are present in certain freshwater and marine fishes, but this enzyme is readily denatured with heating<ref name="NRC"/>. Additionally sulphite preservatives in meats can degrade thiamin resulting in clinical signs of deficiency<ref>Studdert VP and Labuc RH. Thiamin deficiency in cats and dogs associated with feeding meat preserved with sulphur dioxide. Aust Vet J 1991;68:54-57.</ref>. Thiamin is particularly sensitive to degradation with increased temperature especially under alkaline conditions, such as can occur during canned foods production. This higher rate of thiamin degradation requires commercial pet food manufacturers to monitor and supplement thiamin according to expected losses.

==Toxicity==

==Toxicity==

==Dietary Sources==

==Dietary Sources==

Thiamin is naturally occurring in nuts and seeds, muscle and organ meats (especially liver and kidney), yeast, and pulses (e.g., legumes). It is also supplemented into all commercially-prepared complete and balanced dog and cat foods.

Thiamin is naturally occurring in nuts and seeds, muscle and organ meats (especially liver and kidney), yeast, and pulses (e.g. legumes). It is also supplemented into all commercially-prepared complete and balanced dog and cat foods.

==Diagnosing Thiamin Deficiency==

==Diagnosing Thiamin Deficiency==

Diagnosis of thiamine deficiency is based on measurement of low erythrocyte transketolase activity or low plasma thiamine phosphorylated esters serum [[Nutrition Glossary#Retinol|retinol]], though not routinely tested through veterinary reference laboratories. Submission of samples to a human reference laboratory may be possible, though often concurrent submission of normal reference samples is required. Magnetic resonance imaging (MRI) images show changes consistent with thiamine deficient grey matter degeneration.  

Diagnosis of thiamine deficiency is based on measurement of low [[Erythrocytes|erythrocyte]] transketolase activity or low plasma thiamine phosphorylated esters serum [[Nutrition Glossary#Retinol|retinol]], though not routinely tested through veterinary reference laboratories. Submission of samples to a human reference laboratory may be possible, though often concurrent submission of normal reference samples is required. Magnetic resonance imaging (MRI) images show changes consistent with thiamine deficient grey matter degeneration.  

 

Diagnosis is also made on clinical signs consistent with deficiency, evaluation of diet, and response to parenteral thiamine supplementation.

Diagnosis is also made on clinical signs consistent with deficiency, evaluation of diet, and response to parenteral thiamine supplementation.

==References==

==References==

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[[Category:Vitamins]]

[[Category:Vitamins]]