NOS3 Glu298Asp - Nitric Oxide and Cardiovascular Health
Endothelial nitric oxide synthase (eNOS), encoded by the NOS3 gene, produces nitric
oxide (NO) in the lining of blood vessels. Nitric oxide is one of the most important
molecules in cardiovascular biology - it relaxes blood vessel walls, prevents
blood clots from forming, and reduces inflammation in the arterial lining.
The Mechanism
The Glu298Asp | Glutamic acid to aspartic acid at position 298 variant (rs1799983) replaces glutamic acid with aspartic acid at
position 298 of the eNOS protein. The T allele (Asp) makes the enzyme more
susceptible to cleavage and degradation, reducing the steady-state amount of
functional eNOS in endothelial cells. Less enzyme means less nitric oxide
production, which can lead to stiffer blood vessels, higher blood pressure, and
increased oxidative stress.
The Uncoupling Problem
When eNOS is impaired, it can become "uncoupled" | Uncoupled eNOS produces harmful superoxide instead of beneficial nitric oxide - instead of producing beneficial
nitric oxide, it generates superoxide, a harmful reactive oxygen species. This
switches the enzyme from being protective to actively damaging. Adequate levels
of BH4 | BH4 is an essential cofactor that keeps eNOS in its coupled, NO-producing state (tetrahydrobiopterin), a critical cofactor, help prevent uncoupling.
The Evidence
A large meta-analysis | Casas JP et al. Endothelial Nitric Oxide Synthase Genotype and Ischemic Heart Disease. Circulation, 2004 of 26 studies involving 23,028 individuals confirmed that the TT genotype
is associated with increased risk of ischemic heart disease (OR 1.31, 95% CI 1.13-1.51).
A subsequent meta-analysis of 60 studies | Association between eNOS rs1799983 polymorphism and hypertension. BMC Cardiovasc Disord, 2021
involving 14,185 hypertension cases and 13,407 controls found significant associations
under all genetic models (TT vs GG: OR 1.80, 95% CI 1.41-2.31). The effect is
more pronounced when combined with the NOS3 promoter variant (rs2070744) and lifestyle
factors like smoking, sedentary behavior, and poor diet.
Practical Implications
Dietary nitrates from beets, spinach, and arugula can boost NO production through
an alternative pathway | Oral bacteria convert dietary nitrate to nitrite, which is then reduced to NO in the acidic stomach environment that bypasses eNOS entirely. Regular aerobic exercise is
one of the most potent stimulators of eNOS activity and NO production. Vitamin C
and other antioxidants help prevent eNOS uncoupling by supporting BH4 recycling.
All Genotypes
Normal nitric oxide production
Your NOS3 enzyme produces nitric oxide normally. Nitric oxide is crucial for blood vessel health, blood pressure regulation, and cardiovascular function. About 36% of Europeans share this genotype.
Mildly reduced nitric oxide production
You carry one variant that reduces nitric oxide production. When NO production is low, the enzyme may produce superoxide (a harmful oxidant) instead. About 48% of Europeans share this genotype.
Significantly reduced nitric oxide production
You have two NOS3 variants. Nitric oxide production is impaired, increasing cardiovascular risk (OR 1.31 for ischemic heart disease, OR 1.80 for hypertension). About 16% of Europeans share this genotype.