Step by Step
TPP
Thiamine pyrophosphate (TPP) — the coenzyme form
Thiamine (B1) is converted to thiamine pyrophosphate (TPP) — an essential cofactor for three key enzymes: (1) Pyruvate dehydrogenase (PDH): pyruvate → acetyl-CoA. (2) α-Ketoglutarate dehydrogenase (α-KGDH): α-KG → succinyl-CoA (Krebs cycle). (3) Transketolase: pentose phosphate pathway (PPP). Without TPP, carbohydrate metabolism fails — especially critical for the brain (obligate glucose user).
Memory trick: TPP powers Three Processes: PDH, α-KGDH, Transketolase.
Wer
Wernicke's encephalopathy
Wernicke's encephalopathy: acute B1 deficiency — classic triad: Confusion (encephalopathy), Ophthalmoplegia (eye movement abnormalities), Ataxia (gait imbalance). Caused by: alcoholism (most common — alcohol impairs absorption and utilization), hyperemesis gravidarum, malnutrition, bariatric surgery. Treat with IV thiamine BEFORE glucose (glucose infusion without thiamine can precipitate or worsen Wernicke's).
Memory trick: Wernicke's = COA: Confusion, Ophthalmoplegia, Ataxia.
Kor
Korsakoff syndrome
Korsakoff syndrome: chronic sequela of untreated Wernicke's. Characterized by: anterograde amnesia (can't form new memories), confabulation (fabricates memories to fill gaps), relatively preserved other cognitive functions. Mammillary body damage (visible on MRI). Together = Wernicke-Korsakoff syndrome. Difficult to reverse — prevention is critical.
Ber
Beriberi — peripheral manifestation
Wet beriberi: B1 deficiency → cardiac failure (high-output heart failure) + edema. Dry beriberi: peripheral neuropathy (ascending, symmetric). Infantile beriberi: in breastfed infants of thiamine-deficient mothers. Classic in populations eating polished white rice (milling removes thiamine from bran layer). Thiamine deficiency raises pyruvate and lactate → lactic acidosis.
Applied Walkthrough
1
An alcoholic patient presents to the ER confused, with nystagmus and unsteady gait — Wernicke's triad. IV glucose is ordered.
2
STOP — glucose given without thiamine can precipitate fulminant Wernicke's (glucose drives thiamine-dependent reactions, depleting remaining stores). IV thiamine FIRST.
3
With thiamine: ophthalmoplegia resolves in hours-days. Ataxia over days-weeks. Confusion may persist (if Korsakoff's established). Mammillary body damage = permanent memory loss.
4
In Asia: a patient eating only polished white rice develops ascending peripheral neuropathy and weakness — dry beriberi from thiamine deficiency. Restoration of brown rice or thiamine supplements cures it.
Exam Application
Exams test TPP as the coenzyme, the three enzyme systems requiring it (PDH, α-KGDH, transketolase), Wernicke's triad (confusion, ophthalmoplegia, ataxia), the critical rule of giving thiamine BEFORE glucose, Korsakoff's syndrome (anterograde amnesia + confabulation), and beriberi (wet = cardiac, dry = neuropathy).
⚠ Common Trap
The single most dangerous clinical trap: giving IV glucose to a thiamine-deficient patient WITHOUT thiamine first. This drives thiamine-dependent pathways, depleting the last reserves and precipitating acute Wernicke's. Always give thiamine before glucose in any malnourished or alcoholic patient. This is a life-or-death clinical point.
✓ Quick Self-Check
1. What coenzyme does thiamine form?
Thiamine pyrophosphate (TPP).
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2. Name the three enzymes that require TPP.
Pyruvate dehydrogenase (PDH), α-ketoglutarate dehydrogenase (α-KGDH), and transketolase.
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3. What is the classic triad of Wernicke's encephalopathy?
Confusion (encephalopathy), Ophthalmoplegia (eye movement abnormalities), and Ataxia — remembered as COA.
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4. Why must thiamine be given BEFORE glucose in a suspected Wernicke's patient?
Glucose administration drives thiamine-dependent reactions (PDH, α-KGDH), depleting remaining thiamine stores and potentially precipitating or worsening Wernicke's encephalopathy.
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5. What distinguishes Korsakoff syndrome from Wernicke's?
Korsakoff is the chronic sequela of untreated Wernicke's — characterized by anterograde amnesia and confabulation due to mammillary body damage.
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