The heart is a special organ that possesses a high efficiency of energy production system to maintain its continuous contraction (consuming ~6 kg ATP/day for a person). Disruption on cardiac energy metabolism is a risk to developing cardiomyopathy. Our current project investigates the pathological mechanism of cardiac complications associated with propionic acidemia (PA). PA is an autosomal recessive disorder caused by mutations of the PCC gene. Propionyl-CoA Carboxylase, the protein encoded by PCC, catalyzes the conversion of propionyl-CoA to methylmalonyl-CoA, which enters the TCA cycle as an anaplerotic fuel. The deficiency of PCC blocks this anaplerosis and accumulates propionyl-CoA in tissue. A quarter or higher of PA patients develop cardiac diseases which have a high mortality. Our goal is to reveal how PCC deficiency disturbs cardiac energy metabolism and induces cardiac dysfunction.