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==What is Vitamin B9 (Folic Acid)?==

==What is Vitamin B9 (Folic Acid)?==

Vitamin B9, also called folic acid, is an '''essential water-soluble vitamin'''. Dietary folic acid is hydrolysed by intestinal brush border enzymes and absorbed into the enterocyte by both carrier-mediated transport and passive diffusion. Folic acid is further metabolised within the enterocyte to 5-methyl-tetrahydrofolate and released into the portal circulation. Circulating 5-methyl-tetrahydrofolate is then taken up by the liver where it is either retained or released back into circulation. Folic acid derivatives are filtered by the renal tubules, with active reabsorption during periods of low intake.

Vitamin B₉, also called folic acid, is an '''essential water-soluble vitamin'''. Dietary folic acid is hydrolysed by intestinal brush border enzymes and absorbed into the enterocyte by both carrier-mediated transport and passive [[Diffusion - Physiology|diffusion]]. Folic acid is further metabolised within the enterocyte to 5-methyl-tetrahydrofolate and released into the portal circulation. Circulating 5-methyl-tetrahydrofolate is then taken up by the [[Liver - Anatomy & Physiology|liver]] where it is either retained or released back into circulation. Folic acid derivatives are filtered by the [[Nephron Microscopic Anatomy#Proximal Tubule|renal tubules]], with active reabsorption during periods of low intake.

==Why is it Important?==

==Why is it Important?==

==Roles in the Body==

==Roles in the Body==

===Amino Acid Metabolism===

#'''Amino Acid Metabolism''': Folic acid cofactors are used in the inter-conversion of [[Methionine and Cysteine - Nutrition#What are Methionine and Cysteine?|serine]] and [[Taurine - Nutrition#Roles in the Body|glycine]], [[Histidine - Nutrition|histidine]] catabolism, and the regeneration of [[Methionine and Cysteine - Nutrition|methionine]] via donation of a methyl group to homocysteine.<ref name ="Shane">Shane B. (2000) '''Folic Acid, Vitamin B12, and Vitamin B6. In Biochemical and physiological aspects of human nutrition. '''2000 Philadelphia, PA: WB ''Saunders Company'' p. 484-500.</ref>

Folic acid cofactors are used in the inter-conversion of [[Methionine and Cysteine - Nutrition#What are Methionine and Cysteine?|serine]] and [[Taurine - Nutrition#Roles in the Body|glycine]], [[Histidine - Nutrition|histidine]] catabolism, and the regeneration of [[Methionine and Cysteine - Nutrition|methionine]] via donation of a methyl group to homocysteine.<ref name ="Shane">Shane B. (2000) '''Folic Acid, Vitamin B12, and Vitamin B6. In Biochemical and physiological aspects of human nutrition. '''2000 Philadelphia, PA: WB ''Saunders Company'' p. 484-500.</ref>

#'''Nucleotide Synthesis''': Folic acid derivatives are required for purine synthesis and also act as cofactors for thymidylate synthase and dihydrofolate reductase used in synthesis of thymine.<ref name="Shane" /> Thymidylate synthase and dihydrofolate reductase have high expression in replicating tissue.  

 

#'''Therapeutic Target''': The folate antagonist methotrexate, which is used to treat certain types of [[Neoplasia - Pathology|cancers]] is a selective inhibitor of dihydrofolate reductase.

===Nucleotide Synthesis===

Folic acid derivatives are required for purine synthesis and also act as cofactors for thymidylate synthase and dihydrofolate reductase used in synthesis of thymine.<ref name="Shane" /> Thymidylate synthase and dihydrofolate reductase have high expression in replicating tissue.  

 

===Therapeutic Target===

The folate antagonist methotrexate, which is used to treat certain types of cancers is a selective inhibitor of dihydrofolate reductase.

==Consequences of Folic Acid Deficiency==

==Consequences of Folic Acid Deficiency==

===Dogs===

===Dogs===

Folic acid deficiency during gestation can result in [[Cleft Palate|cleft palate]] in puppies.<ref>Elwood JM and Calquhoun TA. (1997) '''Observations on the prevention of cleft palate in dogs by folic acid and potential relevance to humans.''''' New Zeal Vet J'' 1997;45:254-256.</ref><ref>Domoslawska A, ''et al.'' (2013)''' Oral folic acid supplementation decreases palate and/or lip cleft occurrence in Pug and Chihuahua puppies and elevates folic acid blood levels in pregnant bitches. '''''Pol J Vet Sci'' 2013;16:33-37.</ref> Puppies fed folic acid deficient diets experience poor growth and chronic folic acid deficiency in adult can result in low haemoglobin and haematocrit concentrations.<ref name="NRC">National Research Council (NRC) (2006)''' Vitamins. In Nutrient Requirements for Dogs and Cats.''' 2006 ''Washington, DC: National Academies Press ''p.227-230.</ref>

Folic acid deficiency during gestation can result in [[Cleft Palate|cleft palate]] in puppies.<ref>Elwood JM and Calquhoun TA. (1997) '''Observations on the prevention of cleft palate in dogs by folic acid and potential relevance to humans.''''' New Zeal Vet J'' 1997;45:254-256.</ref><ref>Domoslawska A, ''et al.'' (2013)''' Oral folic acid supplementation decreases palate and/or lip cleft occurrence in Pug and Chihuahua puppies and elevates folic acid blood levels in pregnant bitches. '''''Pol J Vet Sci'' 2013;16:33-37.</ref> Puppies fed folic acid deficient diets experience poor growth and chronic folic acid deficiency in adult can result in low haemoglobin and [[haematocrit]] concentrations.<ref name="NRC">National Research Council (NRC) (2006)''' Vitamins. In Nutrient Requirements for Dogs and Cats.''' 2006 ''Washington, DC: National Academies Press ''p.227-230.</ref>

===Cats===

===Cats===

Kittens fed folic acid deficient diets experience decreased growth rate and megablastic anaemia.<ref name="NRC" /> There are no published reports of folic acid deficiency in adult cats.

Kittens fed folic acid deficient diets experience decreased growth rate and megablastic [[Regenerative and Non-Regenerative Anaemias|anaemia]].<ref name="NRC" /> There are no published reports of folic acid deficiency in adult cats.

==Toxicity==

==Toxicity==

[[Category:Vitamins]]

[[Category:Vitamins]]

[[Category:To Do - Nutrition]]

[[Category:To Do - Nutrition]]

[[Category:To Do - Nutrition GGP]]

[[Category:To Do - Nutrition preMars]]