What gene is involved in alcohol flushing?

• A. GABRA6
• B. ALDH5A1
• C. ADH1B
• D. CYP2E1

Answer: (A)

Alcohol flushing occurs when acetaldehyde, a toxic intermediate in alcohol metabolism, builds up because the enzyme that clears it is not working well. The gene that controls this detoxifier is ALDH2, which encodes aldehyde dehydrogenase 2 in the mitochondria. A common variant, ALDH2*2, dramatically reduces this enzyme’s activity, so acetaldehyde accumulates after drinking and triggers the characteristic flushing, warmth, rapid pulse, and nausea.

The other genes listed don’t directly explain the flush. GABRA6 encodes a GABA receptor subunit, not involved in acetaldehyde breakdown. ALDH5A1 is involved in GABA metabolism, not the clearance of acetaldehyde. ADH1B influences how quickly ethanol is converted to acetaldehyde (affecting how much acetaldehyde is produced), and CYP2E1 metabolizes ethanol via a different pathway—these can affect overall exposure but the flush itself is classically due to ALDH2 deficiency.