PDP1 and liver disorder: Additionally, as an essential metabolic intermediate and a key regulator of energy production, citric acid, which inhibits phosphate fructose kinase 1 (PFK1), pyruvate kinase (PK), pyruvate dehydrogenase (PDH) and succinate dehydrogenase (SDH), was remarkably increased in liver disease groups, consistent with its effect of negative regulation on glycolysis and the TCA cycle (Fig. 6)31.