The improvement effect of L-Lys as a chemical chaperone on STZ-induced diabetic rats, protein structure and function

Background L-Lysine (L-Lys) has been known as an inhibitor of protein glycation; however, its long-term use for diabetes treatment considering different aspects of diabetic complication is not seen in the literature. In addition, the effect Of L-Lys, as a chemical chaperone, was considered on protein folding and activity. Methods The streptozotocin-induced diabetic rats were used as a model of diabetes. Normal and diabetic rats were studied for 5 months with and without 0.1% of L-Lys in drinking water. Serum glucose, advanced glycation end product (AGES), haemoglobin A(1C) (HbA(1c)), triglyceride, total cholesterol, HDL-cholesterol, antioxidant activity, advanced oxidation protein products, fasting insulin level and body weight were determined at 4-week intervals. Heat shock protein (HSP)70, Lecithin: cholesterol acyl transferase (LCAT) and paraoxonase activity were determined I week after diabetes induction (time 0), and after 3 and 5 months. The structure of glycated and normal serum albumin (Alb) in the presence and absence of L-Lys was also investigated in an in vitro study using spectrofluorometry and circular dichroism (CD). Results We found that L-Lysine therapy prevented diabetic- induced increases in Glc, AGE, HbA(1c) triglyceride, total- and LDL- cholesterol, and it caused an increase in the decreased antioxidant capacity, HDL-c, HDL functionality and HSP70. L-Lys had no effect on serum insulin level. The conformation of Alb changed due to glycation and L-Lys retained it similar to the native. Conclusions L-Lys, not only as an inhibitor of glycation but also as a chemical chaperone and a protein chaperone inducer, causes effective changes in many parameters of the model animals. However, it is not enough to achieve complete improvement. Copyright (C) 2007 John Wiley & Sons, Ltd.