Intestinal CYP3A4 activity in obesity tends to what?

• A. Decreases
• B. Increases
• C. No change
• D. Fluctuates

Answer: (A)

Intestinal CYP3A4 activity tends to decrease in obesity. The gut wall enzyme CYP3A4 metabolizes many orally given drugs before they reach the bloodstream, shaping first-pass metabolism and oral bioavailability. In obesity, chronic low-grade inflammation and altered gut signaling downregulate CYP3A4 expression in enterocytes. Cytokines such as TNF-α and IL-6, along with changes in nuclear receptor pathways like PXR and CAR, reduce the transcription and activity of this enzyme. Clinically, this means drugs that are substrates of intestinal CYP3A4 can have higher oral bioavailability and greater systemic exposure in individuals with obesity, which can affect dosing and risk of adverse effects.