G6PD and G6PD deficiency: Hence, it is possible that G6PD deficiency-induced cellular dysfunctions could be prevented by supplementation with the micronutrient L-cysteine, which directly boosts the levels of the major antioxidant GSH and increases the transcription of G6PD [32,33,34,35], because G6PD deficiency increases oxidative stress and adversely affects the endothelium by activating TGF-β/Smad/NOX components.