Nutritional regulation of hepatic heme biosynthesis and porphyria through PGC-1α

Inducible hepatic porphyrias are inherited genetic disorders of enzymes of heme biosynthesis. The main clinical manifestations are acute attacks of neuropsychiatric symptoms frequently precipitated by drugs, hormones, or fasting, associated with increased urinary excretion of delta-aminolevulinic acid (ALA). Acute attacks are treated by heme infusion and glucose administration, but the mechanisms underlying the precipitating effects of fasting and the beneficial effects of glucose are unknown. We show that the rate-limiting enzyme in hepatic heme biosynthesis, 5-amino-levulinate synthase (ALAS-1), is regulated by the peroxisome proliferator-activated receptor gamma coactivator 1 alpha (PGC-1 alpha). Elevation of PGC-1 alpha in mice via adenoviral vectors increases the levels of heme precursors in vivo as observed in acute attacks. The induction of ALAS-1 by fasting is lost in liver-specific PGC-1 alpha knockout animals, as is the ability of porphyrogenic drugs to dysregulate heme biosynthesis. These data show that PGC-1 alpha links nutritional status to heme biosynthesis and acute hepatic porphyria.