Metabolism of Lipids 9 Sections27 LessonsLifetime
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 C, Small 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 Ketone bodies 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
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