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==What is Vitamin B7 (Biotin)?==

==What is Vitamin B7 (Biotin)?==

'''Vitamin B7''', also called '''biotin''', is an '''essential water-soluble vitamin'''. Biotin is actively transported across the intestinal mucosa, with minimal passive diffusion, and is typically found as free biotin in plasma. '''Biotin is not stored in the body and is freely filtered by the renal tubules'''.  

'''Vitamin B₇''', also called '''biotin''', is an '''[[Nutrition Glossary#Essential Nutrients|essential]] water-soluble vitamin'''. Biotin is actively transported across the intestinal mucosa, with minimal passive [[Diffusion - Physiology|diffusion]], and is typically found as free biotin in [[plasma]]. '''Biotin is not stored in the body and is freely filtered by the [[Nephron Microscopic Anatomy#Proximal Tubule|renal tubules]]'''.

==Why is it Important?==

==Why is it Important?==

==Roles in the Body==

==Roles in the Body==

Biotin is an essential component of 4 carboxylase enzymes<ref>Sweetman L. Pantothenic Acid and Biotin. In Biochemical and physiological aspects of human nutrition. 2000 Philadelphia, PA: WB Saunders Company p.529-540.</ref>:

Biotin is an essential component of 4 carboxylase enzymes<ref>Sweetman L. Pantothenic Acid and Biotin. In Biochemical and physiological aspects of human nutrition. 2000 Philadelphia, PA: WB Saunders Company p.529-540.</ref>:

#Pyruvate carboxylase, which converts pyruvate to oxaloacetate (OAA) during carbohydrate metabolism;  

#'''Pyruvate carboxylase''', which converts pyruvate to oxaloacetate (OAA) during [[Carbohydrates Overview - Nutrition|carbohydrate]] metabolism;  

#Acetyl CoA carboxylase, which is the rate limiting enzyme step in conversion of acetyl CoA to malonyl CoA in fatty acid synthesis;  

#'''Acetyl CoA carboxylase''', which is the rate limiting enzyme step in conversion of acetyl CoA to malonyl CoA in [[Fatty Acids Overview - Nutrition|fatty acid]] synthesis;  

#Propionyl CoA carboxylase, which carboxylates propionyl CoA (from amino acid, fatty acid or carbohydrate metabolism) into methylmalonyl CoA; and  

#'''Propionyl CoA carboxylase''', which carboxylates propionyl CoA (from [[Protein Overview - Nutrition|amino acid]], fatty acid or carbohydrate metabolism) into methylmalonyl CoA; and  

# 3-methylcrotonyl CoA carboxylase, which functions in the catabolic pathway for leucine.

# '''3-methylcrotonyl CoA carboxylase''', which functions in the catabolic pathway for [[Branched-Chain Amino Acids - Nutrition|leucine]].

==Consequences of Biotin Deficiency==

==Consequences of Biotin Deficiency==

Naturally occurring biotin deficiencies have not been reported unless accompanied by the feeding of raw egg white. Egg white contains a compound called avadin, which irreversibly binds biotin making it unavailable for physiologic use.

Naturally occurring biotin deficiencies have not been reported unless accompanied by the feeding of raw egg white. Egg white contains a compound called [[Nutrition Glossary#Avadin|avadin]], which irreversibly binds biotin, making it unavailable for physiologic use.

====Dogs:====

====Dogs:====

Dogs fed raw egg white develop hyperkeratosis of the skin and scaling<ref>National Research Council (NRC). Vitamins. In Nutrient Requirements for Dogs and Cats. 2006 Washington, DC: National Academies Press p.230-231.</ref>.

Dogs fed raw egg white develop hyperkeratosis of the skin and scaling<ref name="NRC">National Research Council (NRC). Vitamins. In Nutrient Requirements for Dogs and Cats. 2006 Washington, DC: National Academies Press p.230-231.</ref>.

====Cats:====  

====Cats:====  

Kittens fed raw egg white developed excessive accumulation of ocular, nasal, and salivary secretion, alopecia, achromotrichia, skin scaling, weight loss, and diarrhoea<ref>Carey CJ and Morris JG. Biotin deficiency in the cat and its effect on hepatic propionyl CoA carboxylase. J Nutr 1977;107:330-334.</ref>.

Kittens fed raw egg white developed excessive accumulation of ocular, nasal, and salivary secretion, [[Alopecia and Hypotrichosis|alopecia]], achromotrichia, skin scaling, weight loss, and [[diarrhoea]]<ref>Carey CJ and Morris JG. Biotin deficiency in the cat and its effect on hepatic propionyl CoA carboxylase. J Nutr 1977;107:330-334.</ref>.

==Toxicity==

==Toxicity==

There are no published reports of biotin toxicity in dogs and cats;2 excess intake is freely filtered through the renal tubules.

There are no published reports of biotin toxicity in dogs and cats<ref name="NRC"/>; excess intake is [[:Category:Urine Production|freely filtered through the renal tubules]].

==Dietary Sources==

==Dietary Sources==

High concentrations of naturally occurring biotin are found in meats, dairy products, grains, and pulses (e.g., legumes). Because endogenous microbial synthesis is normally adequate, a dietary supply of biotin is not required. However supplementation may be necessary in situations where intestinal microbial synthesis is comprised, such as long term administration of anti-bacterial agents.

High concentrations of naturally occurring biotin are found in meats, dairy products, grains, and pulses (e.g. legumes). Because endogenous microbial synthesis is normally adequate, a dietary supply of biotin is not required. However supplementation may be necessary in situations where intestinal microbial synthesis is compromised, such as long term administration of [[Antibiotics|anti-bacterial agents]].

==Diagnosing Biotin Deficiency==

==Diagnosing Biotin Deficiency==

==References==

==References==

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[[Category:To Do - Nutrition]]

 

[[Category:Vitamins]]