Question

Following a severe cold which caused a loss of appetite, a 1 -year-old boy was hospitalized with hypoglycemia, hyperammonemia, muscle weakness, and cardiac irregularities. These symptoms were consistent with a defect in the carnitine transport system. Dietary carnitine therapy was tried unsuccessfully, but a diet low in long-chain fatty acids and supplemented with medium-chain triacylglycerols was beneficial. The child was diagnosed with carnitine-acylcarnitine translocase deficiency. The dietary treatment was beneficial because A. the child could get all required energy from carbohydrate. B. the deficiency was in the peroxisomal system so carnitine would not be helpful. C. medium-chain fatty acids \((8-10\) carbons) enter the mitochondria before being converted to their CoA derivatives. D. medium-chain triacylglycerols contain mostly hydroxylated fatty acids. E. medium-chain fatty acids such as \(\mathrm{C}_{8}\) and \(\mathrm{C}_{10}\) are readily converted into glucose by the liver.

Short answer

Answer: The most beneficial effect of the specific diet is that medium-chain fatty acids (8-10 carbons) can enter the mitochondria before being converted to their CoA derivatives, which allows them to bypass the defective carnitine transport system and provide energy to the child.

Step-by-step solution

Understanding the disease

Carnitine-acylcarnitine translocase deficiency is a defect in the carnitine transport system, which plays a critical role in the metabolism of long-chain fatty acids. In this condition, the cells are unable to break down long-chain fatty acids for energy production. This can lead to the various symptoms mentioned in the problem statement.

Studying the options

Now we will look through each option and eliminate options that do not make sense or are unrelated to the problem context. A: Although carbohydrates can provide some energy, it is not enough in this case, since one of the main roles of the carnitine transport system is to metabolize long-chain fatty acids. So this option is not correct. B: This is unrelated to the problem context because the deficiency is not in the peroxisomal system but rather in the carnitine transport system. So this option is not correct either. C: Medium-chain fatty acids can enter the mitochondria without the need for the carnitine transport system, which means that the child's body could metabolize them for energy production. This is an adequate statement on why the treatment was beneficial. D: The hydroxylated fatty acids are unnecessary here, as the important aspect is that the medium-chain triacylglycerols (TAGs) are rich in medium-chain fatty acids, which can bypass the defective carnitine transport system. So this option is not correct. E: The conversion of medium-chain fatty acids into glucose is not the key point here, as the main problem is related to the metabolism of long-chain fatty acids and energy production. This option is not correct either.

Conclusion

Considering the information provided in the problem and the analysis of each option, the correct answer is (C): Medium-chain fatty acids \((8-10\) carbons) enter the mitochondria before being converted to their CoA derivatives. This means that they can bypass the defective carnitine transport system and provide energy to the child.