Heme arginate in AIP acts primarily by which mechanism?

Heme arginate in AIP acts primarily by which mechanism?

• A. Inhibits ALA synthase
• B. Induces ALA synthase
• C. Acts as analgesic
• D. Chelates iron

Answer: (A)

Heme arginate works by providing heme to the liver, which triggers negative feedback that downregulates the enzyme responsible for the first step of heme synthesis. This enzyme, ALA synthase (specifically the hepatic form ALAS1), is rate-limiting, and its inhibition reduces production of the neurotoxic porphyrin precursors ALA and PBG that accumulate in acute intermittent porphyria. By suppressing ALAS1, symptoms improve because the overall flux through the heme pathway decreases. Inducing ALA synthase would worsen the buildup of toxic precursors, so that option isn’t correct. It isn’t an analgesic, and it doesn’t chelate iron.

Heme arginate works by providing heme to the liver, which triggers negative feedback that downregulates the enzyme responsible for the first step of heme synthesis. This enzyme, ALA synthase (specifically the hepatic form ALAS1), is rate-limiting, and its inhibition reduces production of the neurotoxic porphyrin precursors ALA and PBG that accumulate in acute intermittent porphyria. By suppressing ALAS1, symptoms improve because the overall flux through the heme pathway decreases.

Inducing ALA synthase would worsen the buildup of toxic precursors, so that option isn’t correct. It isn’t an analgesic, and it doesn’t chelate iron.