What pathway is affected in VLCFA deficiency that leads to the absence of ketones?

In very long-chain fatty acid (VLCFA) deficiency, the affected pathway is beta-oxidation of fatty acids. Beta-oxidation is the process through which fatty acids are broken down in the mitochondria to produce acetyl-CoA, which can then enter the citric acid cycle to be used for energy or converted into ketone bodies during periods of fasting or low carbohydrate intake.

When beta-oxidation is impaired due to the absence of the enzymes that metabolize VLCFAs, the body is unable to efficiently convert these fatty acids into acetyl-CoA. As a result, there is a significant decrease in the production of ketone bodies, which are crucial for supplying energy during fasting states. Without the ability to generate ketones, the individual can experience hypoketotic hypoglycemia, as ketones serve as an alternative energy source when glucose levels are low.

In summary, the inability to properly metabolize VLCFAs through beta-oxidation leads to the absence of ketones, making this the correct explanation for the deficiency observed in VLCFA metabolism.