Quantification NAD+ and its Metabolites in Mouse Sciatic Nerves
Introduction
The crucial parts of nicotinamide adenine dinucleotide (NAD+) and its metabolites in aging and neurodegeneration have been widely recognized. To spur progress toward biochemical research and interventions targeting aging and neurodegenerative diseases, it is of great significance to accurately quantify NAD+ and its metabolite levels in the NAD+ salvage pathway. Here, a robust and accurate LC-MS/MS method is applied to quantify NAD+ and its metabolites levels in normal and injured mouse sciatic nerve.Limitations of existing methods for quantifying NAD+ and its metabolites
Traditional methods for quantifying NAD+ and its metabolites, such as HPLC-UV, NMR, capillary zone electrophoresis, or colorimetric enzymatic assays, face various challenges in sensitivity, selectivity, and indirect measurement. As for existing LC-MS/MS assays for cellular or tissue NAD+ and its metabolites measurements, there are still many difficulties to overcome, such as extended run times, poor chromatographic retention behavior, and unsatisfactory peak shapes. Moreover, only one to three substances in the NAD+ salvage pathway can be covered by these methods.The modifications of LC-MS/MS method
On the basis of existing LC-MS/MS assays, the modifications regarding the chromatographic conditions, surrogate matrix and MS/MS conditions are conducted. Specifically, 5 μM of methylene phosphonic acid is employed as the mobile phase additive, which explicitly promotes the signal intensity and peak shape. Given the relatively clean and simple nature of never samples and their small size, ultrapure water is tested as a substitute matrix. Instead of hydrophilic interaction liquid chromatography column and hypercarb column, the Waters Atlantis Premier BEH C18 AX column is utilized, whose unique MaxPeak HPS high-performance surface technology (passivating the column inner wall, eliminating metal surface) enables the high reproducibility, peak symmetry, and baseline separation of all analytes. Besides, MS conditions are optimized to minimize the NAD+ interference signal in the cyclic adenosine diphosphate ribose (cADPR) channel while maintaining the response of cADPR and nicotinamide mononucleotide (NMN), with 4000V for ion spray voltage, 450℃ for turbo heater temperature, 50 psi for Gas 1, 50 psi for Gas 2, 30 psi for curtain gas, and 12 psi for collision gas.
Representative chromatogram of nerve samples (normal vs injured)
All five analytes achieve baseline separation, where cADPR is a sensitive biomarker in the neurodegeneration model. Herein, sciatic nerve axotomy induces axonal degeneration, leading to reduced NAD+ level and elevated NMN level in the injured nerves, resulting in about a 2-fold increase in the NMN/NAD+ ratio. Simultaneously, the levels of nicotinamide (NAM) and adenosine diphosphate ribose (ADPR), are decreased by about 2-fold, while cADPR level is increased by more than 8-fold. These results are consistent with those of previously reported research, verifying the accuracy of this modified LS-MS/MS method in quantifying NAD+ and its metabolites.
Conclusion
This modified LC-MS/MS method enables effective baseline separation of NAD+, NMN, NAM, ADPR, and cADPR within a brief runtime of 5 min, which is contributive to early diagnoses of various neurological disorders and drug development for aging and neurodegenerative diseases.Reference
Ma Y, Deng L, Du Z. Development and validation of an LC-MS/MS method for quantifying NAD+ and related metabolites in mice sciatic nerves and its application to a nerve injury animal model. J Chromatogr A. doi:10.1016/j.chroma.2024.464821BONTAC NAD
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