Pyrroloquinoline Quinone: Its Profile, Effects on the Liver and Implications for Health and Disease Prevention

Abstract Antioxidant supplementation can reverse hepatic steatosis, suggesting dietary antioxidants might have potential as therapeutics for nonalcoholic fatty liver disease (NAFLD) or nonalcoholic steatohepatitis (NASH). An extraordinarily potent dietary antioxidant is pyrroloquinoline quinone (PQQ). PQQ is a ubiquitous, natural, and essential bacterial cofactor found in soil, plants, and interstellar dust. The major source of PQQ in mammals is dietary; it is common in leafy vegetables, fruits, and legumes, especially soy, and is found in high concentrations in human and mouse breast milk. This chapter reviews chemical and biological properties enabling PQQ's pleiotropic actions, which include modulating multiple signaling pathways directly (NF-κB, JNK, JAK-STAT) and indirectly (Wnt, Notch, Hedgehog, Akt) to improve liver pathophysiology. The role of PQQ in the microbiome is discussed, as PQQ-secreting probiotics ameliorate oxidative stress–induced injury systemwide. A limited number of human trials are summarized, showing safety and efficacy of PQQ.