Description
Cysteine proteinase inhibitors, cystatins superfamily, have been identified in animals, plants and protozoa. All cystatins inactivate lysosomal cysteine proteinases, e.g. cathepsin B, H, K, L and S as well as some structurally related plant proteinases, such as papain and actinidin. Human cystatin C is produced at a constant rate by all nucleated body cells and occurs in all body fluids abundantly. It is a non-glycosilated basic single-chain protein consisting of 120 amino acids with a molecular weight of 13.36 kDa and is characterized by two disulfide bonds in the carboxy-terminal region. The protein is encoded by the CS73 gene located on the short arm of chromosome 20. Biological function of human cystatin C, and its role in various pathological states, has been the subject of numerous studies. Imbalance between cystatin C and cysteine proteinases is associated with diseases such as inflammation, renal failure, cancer, Alzheimer disease, multiple sclerosis and hereditary cystatin C amyloid angiopathy. Its increased level has been found in patients with autoimune diseases, with colorectal tumors and metastases, patients with inflammation and in patients on dialysis. Serum cystatin C concentration correlates negatively with glomerular filtration rate (GFR) as well as or better than creatinine, therefore was recently proposed as a new, very sensitive, marker of changes in GFR. On the other hand, low levels of cystatin C come along the breakdown of the elastic laminae and, subsequently, the atherosclerosis and abdominal aortic aneurysm, as indicate latest publications. Results make evident association of cystatin C levels with the incidence of myocardial infarction, coronary death and angina pectoris. Furthermore, cystatin C correlates with triglycerides, LDL-cholesterol, BMI and age of individuals. Thus, low concentration of cystatin C presents a risk factor for secondary cardiovascular events