Neuronal NAD+ decline in Alzheimer's disease follows a spatially heterogeneous pattern, with cortical and hippocampal neurons exhibiting earlier and more severe depletion than subcortical populations due to differential expression of the NMN transporter SLC12A8 (solute carrier family 12, member 8). This hypothesis proposes that enhancing NMN import into cortical neurons via SLC12A8 agonism or direct NMN intranasal delivery, combined with concurrent SIRT1 activation through small-molecule STAC compounds, achieves superior senescence reversal compared to NMN or NR supplementation alone. The mechanistic prediction is that SLC12A8-mediated NMN transport bypasses the rate-limiting steps of extracellular NMN dephosphorylation by ENPP1, directly supplying the neuronal NAD+ salvage pathway. In amyloid-beta oligomer (Aβ42) treated primary cortical neuron cultures, NMN supplementation partially restores mitochondrial membrane potential (ΔΨm) and reduces SA-β-gal positivity, but SLC12A8 overexpression combined with NMN fully recapitulates the non-senescent phenotype.
...Curated pathway from expert analysis
flowchart TD
A["Cortical Hippocampal NAD+ Decline<br/>SLC12A8 Differential Expression"]
B["ENPP1 Rate-Limiting Step<br/>Extracellular NMN Dephosphorylation"]
C["SLC12A8 NMN Transporter<br/>Direct Neuronal NMN Import Bypass"]
D["Intracellular NAD+ Salvage Pathway<br/>Substrate Supply Restored"]
E["SIRT1 Activation via STAC Compounds<br/>SRT2104 Deacetylase Activity"]
F["PGC1alpha Deacetylation<br/>Mitochondrial Biogenesis Program"]
G["Mitochondrial Membrane Potential Restored<br/>SA-beta-gal Positivity Reduced"]
H["Cortical Neuron Senescence Reversal<br/>Cognitive Function Preservation"]
A --> C
B -.->|"rate-limiting, bypassed"| C
C --> D
D --> E
E --> F
F --> G
G --> H
style C fill:#1a237e,stroke:#4fc3f7,color:#4fc3f7
style H fill:#1b5e20,stroke:#a5d6a7,color:#a5d6a7No linked papers recorded for this hypothesis yet.
No curated PDB or AlphaFold mapping for SLC12A8 yet. Search RCSB →
No curated ClinVar variants loaded for this hypothesis.
Run scripts/backfill_clinvar_variants.py to fetch P/LP/VUS variants.
No DepMap CRISPR Chronos data found for SLC12A8,SIRT1,SRT2104,NMN,SIRT3.
Run python3 scripts/backfill_hypothesis_depmap.py to populate.
No resource usage or linked notebooks recorded for this hypothesis yet.
| Prediction | Predicted | Observed | Status | Conf |
|---|---|---|---|---|
| IF 5xFAD mice (3-month-old, both sexes) receive intranasal NMN (100 mg/kg, 5 days/week) combined with oral SRT2104 (30 mg/kg, daily) for 8 weeks, THEN spatial memory latency in Morris water maze will | MWM escape latency ≤25 seconds (vs ≥40s vehicle); cortical FDG SUVR ≥1.15 (vs ≤0.95 vehicle); cortical NAD+ ≥2.5 pmol/mg (vs ≤1.5 pmol/mg vehicle) | — no observation — | pending | 0.55 |
| IF primary cortical neurons are transfected with SLC12A8 overexpression vector and treated with NMN (500 μM) for 48 hours following Aβ42 oligomer (500 nM) exposure for 24 hours, THEN intracellular NAD | NAD+ concentration ≥1.8 pmol/μg protein; TMRE MFI ≥85% of untreated controls; SA-β-gal positive cells ≤15% | — no observation — | pending | 0.65 |