Vitamin B1

  • Also called thiamine.
  • Function
    • In thiamine pyrophosphate (TPP), a cofactor for several dehydrogenase enzyme reactions:
      • α-ketoglutarate dehydrogenase (TCA cycle)
      • Transketolase (HMP shunt)
      • Branched-chain ketoacid dehydrogenase (catabolism of branched chain amino acids leucine, isoleucine & valine)
      • Pyruvate dehydrogenase (links glycolysis to TCA cycle)
      • Think ATBP
  • Deficiency:
    • Impaired glucose breakdown → ATP depletion worsened by glucose infusion (increased metabolites of glucose); highly aerobic tissues (eg, brain, heart) are affected first.
    • In alcoholic or malnourished patients, give thiamine before dextrose to ↓ risk of precipitating Wernicke encephalopathy.
    • Diagnosis made by ↑ in RBC transketolase activity following vitamin B1 administration.
    • Spell beriberi as Ber1Ber1 to remember vitamin B1.
    • Wernicke-Korsakoff syndrome
      • Wernicke syndrome (classic triad)):
        • Confusion: Disorientation, apathy, decreased attention span. Responds well to treatment.
        • Ophthalmoplegia: Damage to CN III, IV, and vestibular nuclei. Rapidly reversible.
        • Ataxia: Damage to cerebellar cortex, vestibular nuclei. Takes longer to resolve, may be permanent.
      • Korsakoff syndrome: Damage to anterior and medial dorsal nucleus of thalamus, mammillary bodies.
        • Confabulation (when unsure of a fact, will fill in with a fabricated story that they themselves believe to be true)
        • Personality change
        • Memory loss, anterograde amnesia (permanent).
    • Dry beriberi—polyneuropathy, symmetrical muscle wasting.
    • Wet beriberi—high-output cardiac failure (dilated cardiomyopathy), edema.

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