This study proposed that the Slc12a8 gene encodes a specific NMN transporter, based on cell experiments, mouse intestinal biology, gene knockdown and isotopic tracing.
The authors reported that reducing Slc12a8 impaired NMN uptake and that transport showed sodium dependence, supporting direct NMN transport in their experimental systems.
The interpretation became scientifically contested. A subsequent Nature Metabolism Matters Arising by Schmidt and Brenner argued that the evidence did not establish SLC12A8 as an NMN transporter. Both papers should therefore be read together.
Key findings
The study proposed SLC12A8 as a specific NMN transporter.
Slc12a8 knockdown reduced NMN uptake in the reported experiments.
Transport was reported as sodium dependent and selective relative to NR.
A later published critique disputed whether the evidence establishes SLC12A8 as an NMN transporter.
What it cannot establish
Cell and mouse evidence, not direct human transport measurements.
Transporter assignment depends on interpretation of genetic, kinetic and tracer data.
A published Matters Arising directly challenged the transporter conclusion.
The question should be presented as scientifically contested rather than settled.
HealthspanX claim boundary: This study does not settle the mechanism of NMN uptake in humans or establish direct intact oral NMN transport into human tissues.
