Cystatin C

Cystatin C is a non-glycosylated protein that belongs to the Cystatin superfamily, a group of proteins known for their ability to inhibit Cysteine proteases. It is encoded by the CST3 gene in humans and is often used as a biomarker of Kidney function.

Function

Cystatin C is a potent inhibitor of lysosomal proteinases (enzymes that break down proteins) and is present in virtually all nucleated cells. As such, it is involved in a variety of biological and pathological processes. It is believed to play a crucial role in the prevention of uncontrolled proteolysis and in the regulation of inflammatory processes.

Clinical significance

Cystatin C has gained interest in the medical field because it is a more precise test of the Glomerular filtration rate (GFR), which is a key indicator of kidney function. Unlike Creatinine, which can be affected by factors such as muscle mass, diet, and medication, Cystatin C levels remain relatively constant, making it a more reliable marker.

In addition to its role in assessing kidney function, elevated levels of Cystatin C have been associated with increased risk of Cardiovascular disease, Diabetes, and Mortality in older adults. It has also been implicated in neurodegenerative diseases such as Alzheimer's disease and Cerebrovascular disease.

Measurement

The measurement of Cystatin C is typically done through a blood test. The results are usually available within a few days. The normal range for Cystatin C levels in the blood is typically between 0.53 and 0.95 milligrams per liter (mg/L), but this can vary depending on the lab that analyzes the test.

See also

• Cysteine proteases
• Kidney function
• Glomerular filtration rate
• Creatinine