In long-chain fatty acid oxidation disorders, which metabolite accumulates in tissues such as palmitate?

• A. Pyruvate
• B. Ketone bodies
• C. Palmitate
• D. Glucose

Answer: (C)

Long-chain fatty acid oxidation disorders block mitochondrial beta-oxidation of long-chain fatty acids. When this breakdown is defective, these fatty acids cannot be used for energy and therefore accumulate in tissues as fatty acyl species. Palmitate is a representative long-chain fatty acid, so it tends to build up in tissues. In contrast, pyruvate or glucose aren’t the accumulating substrates in this scenario, and ketone body production is typically impaired (leading to low ketones rather than accumulation) because the acetyl-CoA from fatty acid oxidation is not adequately generated. So the metabolite that accumulates in tissues is palmitate.