Functions

Active form: thiamine pyrophosphate (TPP) In thiamine pyrophosphate (TPP), a cofactor for several dehydrogenase enzyme reactions (Be APT):

• Branched-chain ketoacid dehydrogenase (Maple syrup urine disease)
• α-Ketoglutarate dehydrogenase (TCA cycle)
• Pyruvate dehydrogenase (links glycolysis to TCA cycle)
• Transketolase (HMP shunt)

Epidemiology

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Etiology

• Heavy drinking
  • Alcohol damages the lining of the intestine and directly inhibits the transport mechanism that is responsible for thiamine absorption in the intestinal tract.
• Malnutrition, starvation
• Malabsorption
• Malignancy

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Pathophysiology

• Thiamine deficiency → impaired glucose breakdown → ATP depletion → tissue damage that primarily affects highly aerobic tissues (e.g., brain, heart)
• High-dose glucose infusions lead to increased ATP depletion, which can trigger Wernicke encephalopathy.
  • In malnourished individuals and chronic alcohol users/heavy drinkers, thiamine should be administered before glucose infusions.

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Clinical features

• Beriberi (脚气病): inadequate thiamine uptake due to malnutrition, heavy drinking, or increased demand (e.g., hyperthyroidism, pregnancy)
  • Dry beriberi
    • Symmetrical peripheral neuropathy (sensory and motor)
    • Progressive muscle wasting
    • Paralysis
    • Confusion
  • Wet beriberi
    • High-output cardiac failure (due to systemic vasodilation)
    • Dilated cardiomyopathy
    • Cardiomegaly
    • Edema
• Wernicke encephalopathy

Tip

In malnourished or alcohol-dependent patients, always administer thiamine before giving dextrose to decrease the risk of precipitating or exacerbating Wernicke encephalopathy.

Mnemonic

Vitamin B1 deficiency causes Ber1Ber1.

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Diagnostics

• Vitamin B1 administration → ↑ RBC transketolase activity

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Treatment

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