Dirty Medicine: Disorders of Fructose Metabolism

Introduction

• Focus: Disorders of fructose metabolism
• Structure:
  • Biochemical pathway of fructose breakdown
  • Discussion of two diseases from enzyme deficiencies
• Diseases:
  • Benign disorder
  • Severe disorder

Biochemical Pathway

• Starting Point: Fructose
• Conversion:
  • Fructose to Fructose-1-Phosphate by Fructokinase
    • Kinase: Adds a phosphate group
  • Fructose-1-Phosphate to Glyceraldehyde or DHAP by Aldolase B
    • Both can form Glyceraldehyde-3-Phosphate (G3P)
• Pathway:
  • Fructose → Fructose-1-Phosphate → Glyceraldehyde/DHAP → G3P → Glycolysis

Understanding the Pathway

• Carbohydrates: Enter glycolysis to yield ATP
• Fructose Breakdown: Slower than glucose
• Mnemonic:
  • "Fruits are filled with fructose, they are goddamn juicy"
    • Fruits: Fructose
    • Filled: Fructokinase
    • Fructose: Fructose-1-Phosphate
    • Are: Aldolase B
    • Goddamn: Glyceraldehyde
    • Juicy: Glyceraldehyde-3-Phosphate

Disease 1: Fructokinase Deficiency

• Symptoms:
  • Fructose in blood (Fructosemia) and urine (Fructosuria)
  • Autosomal recessive
  • Benign with minimal symptoms
• Mnemonic: "Fructose kind-a deficiency" (Benign)

Disease 2: Aldolase B Deficiency (Hereditary Fructose Intolerance)

• Pathophysiology:
  • Accumulation of Fructose-1-Phosphate
  • Depletion of ATP
  • Inhibition of Gluconeogenesis and Glycogenolysis
  • Results in hypoglycemia after fructose ingestion
• Symptoms:
  • Severe hypoglycemia
  • Cannot consume fructose, glucose, or sucrose
• Mnemonic: "Here you are entirely" (Severe)

Summary

• Fructokinase Deficiency:
  • Benign, autosomal recessive
  • Mnemonic: "Fructose kind-a deficiency"
• Hereditary Fructose Intolerance:
  • Severe, hypoglycemic events
  • Mnemonic: "Here you are entirely"
• High-Yield:
  • Know the enzymes involved
  • Understand the pathway and disease mechanisms
  • Utilize mnemonics for memorization

Conclusion

• Disorders of fructose metabolism cover enzyme deficiencies leading to benign or severe outcomes. Understanding the biochemical pathway and associated mnemonics is crucial for exams.