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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.
- Muscle aches, weakness, Myoglobinuria.
- Provoked by prolonged exercise especially if fasting.
- Biopsy shows elevated muscles TAGs.
- Most common form (autosomal recessive).
- Late onset.
- Similar to CAT deficiency.
- Muscle phosphorylase is defective.
- This results in accumulation of Glycogen in muscles.
- Biopsy shows increased glycogen in muscles.
- 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 C, Small chain below 6C (SCAD).
- When there is deficiency of MCAD, the Medium chain Fatty acids accumulate resulting in disease.
- 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.