Updated: 12/4/2018

Ethanol Metabolism

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Topic
Review Topic
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N/A
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Questions
2
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100%
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Evidence
4
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Topic
Overview
  • Function
    • elimate ethanol (EtOH)
      • CNS depressant/toxin
  • Kinetics
    • NAD+ is limiting reagent
    • alcohol dehydrogenase operates via zero-order kinetics
    • inhibitors 
      • fomepizole inhibits alcohol dehydrogenase
        • antidote for suspected ethylene glycol or methanol poisoning 
      • disulfiram (Antabuse) inhibits acetaldehyde dehydrogenase
        • acetaldehyde accumulates
        • leads to hangover symptoms
        • prescribed to help recovering alcoholics
  • Clinical relevance 
    • ethanol hypoglycemia
      • pathophysiology
        • ↑ in EtOH metabolism → ↑ NADH/NAD+ ratio
        • NADH/NAD+ ratio changes energy generating kinetics
        • lactate favored over pyruvate
          • lactate + NAD+ → pyruvate + NADH
          • no free NAD+ for required conversion
        • glycerol-3-phosphate favored over DHAP
          • G3P + NAD+ → DHAP + NADH
        • malate favored over oxaloacetate
          • malate + NAD+ → OAA + NADH
      • presentation
        • lactic acidosis
          • ↑ lactate
        • fatty liver
          • ↑ G3P results in ↑ synthesis of TGs
    • ethanol + extreme physical exertion
      • severe hypoglycemia
      • EtOH inhibits the Cori cycle by consumption of free NAD+
        • conversion of lactate to glucose in anaerobic metabolism
        • lactic acidosis

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Questions (2)
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(M1.BC.14.1) An 18-year-old male presents to the emergency room smelling quite heavily of alcohol and is unconscious. A blood test reveals severe hypoglycemic and ketoacidemia. A previous medical history states that he does not have diabetes. The metabolism of ethanol in this patient's hepatocytes resulted in an increase of the [NADH]/[NAD+] ratio. Which of the following reaction is favored under this condition?

QID: 106289
1

Pyruvate to acetyl-CoA

13%

(8/60)

2

Citrate to isocitrate

0%

(0/60)

3

Oxaloacetate to malate

57%

(34/60)

4

Oxaloacetate to phosphoenolpyruvate

27%

(16/60)

5

Fumarate to malate

2%

(1/60)

M 1 E

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Evidence (4)
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