YKL-40 is a 40 kD lectin molecule. It is secreted by various cells, including macrophages, vascular smooth muscle cells and giant cells, and the level of YKL-40 is found elevated in both acute (eg. infection) and chronic (eg. rheumatoid arthritis, systemic lupus erythematosus or cirrhosis of the liver) inflammatory processes. The plasma concentration of YKL-40 is elevated in the patients of type 2 diabetes mellitus compared with non-diabetic controls, and is associated with insulin resistance, fasting plasma glucose and plasma IL-6 concentrations. Furthermore, the concentration of YKL-40 is elevated and is associated with the severity of albuminuria in the patients of type 1 diabetes.