Effects of dietary cysteine on blood sulfur amino acid, glutathione, and malondialdehyde concentrations in cats

Objective-To determine effects of dietary cysteine on blood sulfur amino ac ids (SAA), reduced glutathione (GSH), oxidized glutathione (GSSG), and malo ndialdehyde (MDA) concentrations in cats. Animals-12 healthy adult cats. Procedure-Cats were fed diets with a nominal (0.50 g/100 g dry matter [DMI) , moderate (1.00 g/100 g DM), or high (1.50 g/100 g DM) cysteine content in a 3 X 3 Latin square design with blocks of 8 weeks' duration. Venous blood samples were collected after each diet had been fed for 4 and 8 weeks, and a CBC and serum biochemical analyses were performed; poikilocyte, reticulo cyte, and Heinz body counts were determined; and MDA, GSH, GSSG, and SAA co ncentrations were measured. Results-Blood cysteine and MDA concentrations were not significantly affect ed by dietary cysteine content. Blood methionine, homocysteine, and GSSG co ncentrations were significantly increased when cats consumed the high cyste ine content diet but not when they consumed the moderate cysteine content d iet, compared with concentrations obtained when cats consumed the nominal c ysteine content diet. Blood GSH concentrations were significantly increased when cats consumed the moderate or high cysteine content diet. Conclusions-Increased dietary cysteine content promotes higher blood methio nine, homocysteine, GSH, and GSSG concentrations in healthy cats. Clinical Relevance-Supplemental dietary cysteine may be indicated to promot e glutathione synthesis and ameliorate adverse effects of oxidative damage induced by disease or drugs.