Procysteine stimulated gene expression of anabolic factors such as insulin-like growth factor-1, ciliary neurotrophic factor, and cardiotrophin-1[2]. Procysteine supplementation eliminated the aging-associated differences in hepatic GSH and GSH/GSSG ratio. The nSMase activity and ceramide increased in the procysteine-fed mice irrespective of their age. The procysteine-fed aged mice also exhibited hepatic steatosis and triacylglyceride accumulation [3].