In hepatic encephalopathy, what contributes to the symptoms due to amino acid imbalance?

• A. Increased ratio of aromatic amino acids to BCAAs, leading to false neurotransmitters.
• B. Decreased aromatic amino acids.
• C. Increased BCAAs causing excitotoxicity.
• D. No role of amino acids.

Answer: (A)

In hepatic encephalopathy, liver failure causes an increase in aromatic amino acids (phenylalanine, tyrosine, tryptophan) and a decrease in branched-chain amino acids (valine, leucine, isoleucine). This raises the ratio of aromatic to branched-chain amino acids in the blood. These amino acids share the same large neutral amino acid transporter to enter the brain, so when aromatic amino acids predominate, more of them cross into the brain and fewer BCAAs compete for transport. The excess aromatic amino acids are metabolized to neurotransmitter-like amines, producing false neurotransmitters that disrupt normal neuronal signaling and contribute to the cognitive and motor symptoms of HE. The other options don’t fit the typical pattern observed in HE, where aromatic amino acids rise and BCAAs fall, not the reverse or no role for amino acids.