Stabilization and quantitative measurement of nicotinamide adenine dinucleotide in human whole blood using dried...

Nicotinamide adenine dinucleotide (NAD⁺) is a coenzyme essential for energy production. Recently, associations between NAD⁺ and aging-related diseases have been reported, and NAD⁺ precursors that increase NAD⁺ concentration in the body have been acknowledged as anti-aging supplements. However, there have been only a few studies on the link between aging or aging-related diseases and human blood NAD⁺ concentration because NAD⁺ and its precursors are unstable in blood and difficult to measure. Therefore, we aimed to construct a quantitative NAD⁺ measurement method that is simpler than the existing methods. The calibration standards of NAD⁺ showed good linearity (0.9936 to 0.9990) in the range of 0.25 to 200 μM, and the lower limit of quantification was 0.5 to 2 μM. We found that QIAcard FTA DMPK-B maintained NAD⁺ stability of 85% or more for at least 2 weeks at 4 °C and 1 week at room temperature using the dried blood spot method. Additionally, NAD⁺ stability in the blood extraction solution was more than 90% for 2 months. To our knowledge, there has been no report on a quantitative NAD⁺ measurement method in human whole blood that can be performed with as little as 5 μL of blood and can be easily implemented at both medical clinics and private homes. Our simple and convenient method has the potential to become the gold standard for NAD⁺ measurement in blood. It is expected to contribute to the acceleration of research on the correlation between aging or aging-related diseases and NAD⁺ concentration in human blood.