Understanding ADMA, SDMA, and Homoarginine: Key Biomarkers for Cardiovascular and Kidney Health
The inner lining of your arteries is made up of a thin layer of endothelial cells. These cells are in constant contact with your blood and play a crucial role in immunity, blood clotting, and blood pressure regulation. When these endothelial cells become damaged, it increases the risk of cardiovascular disease and kidney failure. Understanding specific biomarkers like ADMA, SDMA, and homoarginine (hArg) can provide essential insights into endothelial function and overall health.
What Are ADMA and SDMA?
ADMA (asymmetric dimethylarginine) is a methylated derivative of the amino acid arginine (Arg). It acts as an endogenous inhibitor of nitric oxide (NO) production by nitric oxide synthase (NOS), making it a key marker of endothelial dysfunction. A closely related compound, SDMA (symmetric dimethylarginine), does not directly inhibit NOS but competes with arginine for cellular uptake, thereby reducing NO availability. SDMA is also recognized as an endogenous marker of kidney function. Even a slight deterioration in renal function can increase cardiovascular risk, making SDMA an important biomarker for early detection.
The Role of Homoarginine (hArg)
Unlike ADMA and SDMA, homoarginine (hArg) is a methylene homolog of arginine and serves as a substrate for NOS. It can enhance NO availability in two key ways:
- Acting as a direct precursor for NO synthesis.
- Increasing intracellular L-arginine levels by inhibiting the enzyme arginase, which competes with NOS.
Because of these properties, hArg plays a positive role in maintaining endothelial function.
What Causes Elevated ADMA and SDMA Levels?
Causes of Elevated ADMA Levels:
- Cardiovascular disease
- Endothelial dysfunction
- Various cancers (breast, colon, lung, gastric)
- Hematopoietic tumors
- Atherosclerosis
- Hypertension
- Type II diabetes
- Chronic coronary artery calcification
- Increased risk of stroke-like episodes
Causes of Elevated SDMA Levels:
- Progressive kidney failure
- Reduced glomerular filtration rate (GFR)
- Chronic kidney disease (CKD)
- Impaired renal function
Plasma SDMA is an early biomarker for progressive kidney failure. It is one of the most sensitive indicators of glomerular filtration rate (GFR) and is included in the International Renal Interest Society (IRIS) CKD guidelines as a complement to creatinine testing. Unlike creatinine, SDMA provides more accurate readings as it is not affected by factors such as age, gender, diet, muscle mass, or medications. In chronic kidney disease (CKD), SDMA levels rise with a GFR reduction of 40-50%, whereas creatinine levels only increase when GFR declines by 70-80%.
The Impact of Low Homoarginine (hArg) Levels
In contrast to elevated ADMA and SDMA levels, low plasma hArg levels are associated with negative cardiovascular outcomes. Reduced hArg levels have been observed in diabetic patients undergoing hemodialysis, patients with peripheral arterial disease, individuals post-ischemic stroke, those referred for coronary angiography, and kidney transplant recipients. Maintaining adequate hArg levels may help support cardiovascular and renal health.
Blood Tests for ADMA, SDMA, and hArg
WHL offers blood tests to measure ADMA, SDMA, and hArg levels. These tests can be ordered individually or as part of a panel. Additionally, tests for nitric oxide (NO) and amino acids are available to provide a comprehensive evaluation of endothelial and renal function.
Conclusion
ADMA, SDMA, and homoarginine are essential biomarkers for assessing endothelial function, cardiovascular health, and kidney function. Elevated ADMA and SDMA levels indicate an increased risk of cardiovascular disease and renal impairment, while low hArg levels are linked to adverse health outcomes. Regular testing can help in early detection and management of these conditions, allowing for better preventive care and treatment strategies.
