Biotin Review

BIOTIN

Egg white injury - eating raw eggs results in hair loss, dermatitis, neuromuscular problems.

Structure:

• Ureido ring
• Thiophene ring
• Valeric acid side chain

SOURCES

Made by bacteria in colon
Major food: liver (21 ug), milk, soy, egg yolk (4ug)

Found free or bound to protein
Egg whites have biotin bound to Avindin which does not release

DIGESTION, ABSORPTION, METABOLISM, and EXCRETION

Protein bound biotin requires pepsin yields free biotin or BIOCYTIN
BIOCYTIN is biotin bound to Lysine, required BIOTINIDASE hydrolysis
Biotinidase Deficiency = inborn error of metabolism

Absorbed passively or by carrier mediation via SHARED MULTIVITAMIN TRANSPORTER (SMVT)
ETOH impairs absorption

In plasma, 80% free biotin, [ ] 200-750 ug/mL
Stored in muscle, liver, brain

FUNCTION/MOA

Coenzyme carrier for transfer of activated bicarbonate to substrates for:

• Fatty acid synthesis
• Gluconeogenesis
• Metabolism of branched chain amino acids
• Role in ELONGASE enzymes that convert the O-6 Linolenic Acid and O-3 A-Linoleic Acid into longer chain fatty acids such as DHA and EPA from ALA

Uses

Blood glucose mgt - improves fasting blood glucose
Ratio of LDL to HDL and TG:HDL
Convert o-3 and o-6 to arachadonic acid and EPA and DHA
Vegetarians should supplement to allow for these long chain PUFA
Hair skin nail problems

RDA

AI 30 ug / d

DEFICIENCY

rare ~ raw eggs

• Neurological - parestesias, ataxia, seizures
• Cutaneous

Risk: GI disorders, Illness with increased need for biotin, medications that interfere with absorption (sulfa, anticonvulsants, antibiotics).

TOXICITY

no TUL

Assessment:

Serum <200 ug/Ml

Urine