The Most Important Pathologies associated with B-Oxidation of fatty acids

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Pathologies associated with Beta oxidation

Myopathic CAT/CPT Deficiency

  • Fatty acids have to go inside the mitochondria for β-oxidation.
  • They do it through the carnitine shuttle.
  • When there is deficiency of CAT/CPT enzyme this cannot happen.
  • This results in CAT deficiency.
  • CAT – Carnitine Acyl Transferase.
  • CPT – Carnitine Palmitoyl Transferse.
  • Both are enzymes.

Clinical Features

  • Muscle aches, weakness, Myoglobinuria.
  • Provoked by prolonged exercise especially if fasting.
  • Biopsy shows elevated muscles TAGs.
  • Most common form (autosomal recessive).
  • Late onset.

Differential Diagnosis

McCardle’s disease

  • Similar to CAT deficiency.
  • Muscle phosphorylase is defective.
  • This results in accumulation of Glycogen in muscles.
  • Biopsy shows increased glycogen in muscles.

MCAD deficiency

  • There can also be LCAD (Long Chain FA CoA Dehydrogenase).
  • Medium Chain fatty acyl CoA dehydrogenase (MCAD) .
  • Most Fatty acids are long chain up to 10-18 C onwards, Medium chain are from 6-10 CSmall chain below 6C (SCAD).
  • When there is deficiency of MCAD, the Medium chain Fatty acids accumulate resulting in disease.

Clinical Features

  • Fasting hypoglycemia as β-oxidation is blocked so there is decrease in gluconeogenesis.
  • No ketone body synthesis as Acetyl CoA is not formed and so KB are not synthesized.
  • C8-10 acyl carnitine in blood.
  • Vomiting – Coma – Death.

This is Autosomal recessive (AR) with variable expression

Dicarboxylic Acidemia (MCAD deficiency)

  • In peroxisomes there is omega oxidation.
  • Due to blockade of β-oxidation, the Fatty acids accumulate and go to peroxisomes where electrons from ω-carbon are removed and these are converted to dicarboxylic acids.
  • This Dicarboxylic acid accumulates in the blood resulting in Dicarboxylic acidemia and then
  • In urine – dicarboxylic aciduria

FOR COMPLETE LESSONS ON LIPID METABOLISM, PLEASE VISIT THE SECTION OF LIPID METABOLISM IN BIOCHEMISTRY II.

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