PRKN and Parkinson disease: Metabolomics studies using iPSC-derived DA neurons from PD patients with Parkin mutations showed that these neurons exhibit high levels of citrate, succinate, malate, glutamate, and lactate, but reduced levels of glucose, pyruvate, and GSH/GSSG ratio, strongly suggesting alterations in the TCA cycle, glucose, and glutathione metabolism (Okarmus et al., 2021).