Masquerading acidosis after cardiopulmonary bypass: a case of propionic acidemia and congenital heart disease

Metabolic perturbations mediated by propionyl-CoA accumulation in organs of mouse model of propionic acidemia

Propionic acidemia (PA) is an autosomal recessive metabolic disorder after gene encoding propionyl-CoA carboxylase, Pcca or Pccb, is mutated. This genetic disorder could develop various complications which are ascribed to dysregulated propionyl-CoA metabolism in organs. However, the effect of attenuated PCC on propionyl-CoA metabolism in different organs remains to be fully understood. We investigated metabolic perturbations in organs of Pcca^-/-(A138T) mice (a mouse model of PA) under chow diet and acute administration of [¹³C₃]propionate to gain insight into pathological mechanisms of PA. With chow diet, the metabolic alteration is organ dependent. l-Carnitine reduction induced by propionylcarnitine accumulation only occurs in lung and liver of Pcca^-/- (A138T) mice. [¹³C₃]Propionate tracing data demonstrated that PCC activity was dramatically reduced in Pcca^-/-(A138T) brain, lung, liver, kidney, and adipose tissues, but not significantly changed in Pcca^-/-(A138T) muscles (heart and skeletal muscles) and pancreas, which was largely supported by PCCA expression data. The largest expansion of propionylcarnitine in Pcca^-/-(A138T) heart after acute administration of propionate indicated the vulnerability of heart to high circulating propionate. The overwhelming propionate in blood also stimulated ketone production from the increased fatty acid oxidation in Pcca^-/-(A138T) liver by lowering malonyl-CoA, which has been observed in cases where metabolic decompensation occurs in PA patients. This work shed light on organ-specific metabolic alternations under varying severities of PA.