Alzheimer's disease (AD) is an irreversible neurodegenerative disease with no effective cure to date, affecting over 50 million patients worldwide. In recent years, researchers have increasingly focused on aberrant alternative RNA splicing events (ASEs) in cells, believing they play a key role in AD pathogenesis.
On November 7, 2025, a study published in Science Advances titled "NAD reverses Alzheimer's neurological deficits via regulating differential alternative RNA splicing of EVA1C" revealed that NAD+ (nicotinamide adenine dinucleotide) significantly improves cognitive function in AD models by regulating the alternative splicing of the key protein EVA1C, providing a novel target for AD treatment.
NAD+ and Aberrant RNA Splicing: An Overlooked Pathogenic Mechanism of AD
What is alternative RNA splicing? Simply put, just as a film editor cuts footage into different versions of a movie, cells "splice" a single gene to produce multiple protein variants. Errors in this process disrupt cellular function.
The research team systematically analyzed the effects of NAD+ precursors—nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN)—on RNA splicing using multiple biological models, including transgenic mice expressing human mutant Tau protein (hTau.P301S) and Caenorhabditis elegans (C. elegans).
Key findings:
- In the hippocampus of AD model mice, the expression of 509 genes was abnormally altered.
- RNA splicing-related genes were significantly downregulated, particularly in splicing types such as exon skipping and intron retention.
- This splicing aberration impaired critical physiological processes including mitochondrial function and synaptic transmission.
NAD+: The "Molecular Doctor" Repairing Splicing Errors
NAD+ is a core molecule in cellular energy metabolism, known as the cell's "power bank." This study is the first to systematically reveal its key role in regulating RNA splicing through two mechanisms:
Mechanism 1: Remodeling the Splicing Landscape
- Supplementing AD mice with NAD+ precursors significantly improved the abnormal expression of 730 genes.
- NAD+ precursors specifically regulated 79 spliceosome-related genes, including core splicing factors such as U1/U2/U4/U5.
Mechanism 2: Activating a Neuroprotective Axis
The team identified a key effector molecule—EVA1C protein. Critical for neuronal development, EVA1C is significantly reduced in the brains of AD patients.
EVA1C: The Key "Switch" for NAD+'s Effects
To verify EVA1C's importance, the team conducted rigorous experiments:
Gene Knockdown Experiment
- Specific knockdown of the Eva1c gene in the mouse hippocampus using AAV virus completely abolished the cognitive improvement effects of NAD+ precursors.
- In the novel object recognition test, memory recovery was significantly impaired in the knockdown group.
Cross-Species Validation
In C. elegans models:
- NAD+ precursors extended the lifespan of AD model worms by 16.84%.
- This lifespan-prolonging effect disappeared when the eva-1 gene was knocked down.
AI Prediction + Experimental Verification: Uncovering Molecular Mechanisms
Combining AlphaFold 3 AI technology, the team predicted the 3D structure of EVA1C and confirmed:
- NAD+ precursors promote the expression of a specific EVA1C isoform with higher binding affinity to the chaperone HSP70 (a cellular "protein quality inspector" involved in clearing misfolded proteins).
- Co-immunoprecipitation verified that NAD+ precursors enhance the interaction between EVA1C and HSP70.
Cross-Species Validation and Clinical Relevance
The team further validated these findings in human brain tissue samples:
- Single-cell RNA sequencing showed high EVA1C expression in oligodendrocytes, suggesting its potential role in myelin maintenance and white matter integrity.
- EVA1C protein levels in AD patients' brain tissue decreased with increasing Braak stages, particularly in neurons.
Outlook: A New Direction for Precision Medicine
This study is the first to systematically reveal the critical role of the NAD+–EVA1C–splicing axis in AD. It explains NAD+'s neuroprotective mechanism not only from an energy perspective but also at the genetic level, providing new ideas for developing precision therapies based on splicing regulation.
Currently, multiple clinical trials targeting NAD+ precursors (e.g., NCT05617508, NCT04430517) are underway. In the future, combining AI and multi-omics data is expected to screen for more efficient splicing-regulating small molecules or oligonucleotide drugs, opening new avenues for treating Alzheimer's and other neurodegenerative diseases.
Reference
Ai R, Mao L, Jin X, et al. NAD+ reverses Alzheimer's neurological deficits via regulating differential alternative RNA splicing of EVA1C. Sci Adv. 2025 Nov 7;11(45):eady9811. doi: 10.1126/sciadv.ady9811. Epub 2025 Nov 7. PMID: 41202143; PMCID: PMC12594206.