L-cysteine is a potent inhibitor of protein glycation on both albumin and LDL, and prevents the diabetic complications in diabetic–atherosclerotic rat

Abstract

The aim of the present study is to investigate the protective effect of l-cysteine (Cys) on protein glycation, and hence, the improvement of diabetic complications. Streptozotocin-induced diabetic rats on an atherogenic diet were used as a model. Two groups of rats, normal and diabetic, were treated with 0.05% of Cys in drinking water for 3months and two others received water only. Some parameters including: glucose, insulin, glycation products, activity of the glyoxalase system, lipid profile, oxidation markers, high sensitivity CRP (Hs CRP) and creatinine in the serum, and protein in the urine of all rats were determined. Furthermore, rat serum albumin and LDL were purified and incubated with glucose in the presence and absence of Cys and the samples were investigated for glycation and oxidation products. Cys showed an inhibitory effect on glycation and oxidation products in both in vivo and in vitro conditions. It reduced glucose, insulin resistance, triglyceride, cholesterol, LDL, Hs CRP and creatinine in the serum; and the proteinuria; furthermore, it increased HDL and glyoxalase system activity in the serum of the diabetic–atherosclerotic rats. Cys reduced all of the risk factors of diabetic complications and showed anti-atherosclerotic potential; thus it is useful in diabetes treatment.