NAMPT (Nicotinamide Phosphoribosyltransferase), also known as visfatin or pre-B cell colony-enhancing factor (PBEF), encodes the rate-limiting enzyme in the NAD+ salvage pathway[1]. NAMPT catalyzes the conversion of nicotinamide (NAM) to nicotinamide mononucleotide (NMN), which is then converted to NAD+ by NMN adenylyltransferases (NMNATs).
NAD+ is an essential cofactor for metabolic enzymes including sirtuins (SIRT1-7), poly(ADP-ribose) polymerases (PARPs), CD38/CD157, and NAD+dependent dehydrogenases. Declining NAD+ levels with age are a hallmark of metabolic dysfunction and neurodegeneration[2]. NAMPT is therefore a critical node linking cellular energetics, protein acetylation status, and neuronal survival in Alzheimer's disease, Parkinson's disease, and amyotrophic lateral sclerosis (ALS)[@rhyu2018].
| Property | Value |
|---|---|
| Gene Symbol | NAMPT |
| Full Name | Nicotinamide Phosphoribosyltransferase |
| Aliases | Visfatin, PBEF, PBEF1 |
| Chromosomal Location | 7q22.3 |
| NCBI Gene ID | 10135 |
| OMIM | 608064 |
| Ensembl ID | ENSG00000105835 |
| UniProt ID | Q99714 |
| Gene Type | Protein Coding |
NAMPT is a homodimeric enzyme (~52 kDa per subunit) that catalyzes the first and rate-limiting step of NAD+ salvage[@rhyu2018]:
Nicotinamide + PRPP (5-phosphoribosyl-1-pyrophosphate) → NMN + PPi
This reaction requires:
The enzyme has two conformations: an open state for substrate binding and a closed state during catalysis. NAMPT activity is regulated by:
NAMPT is the gatekeeper of the NAD+ salvage pathway[1:1]:
The salvage pathway is the predominant NAD+ source in most tissues. In the brain, the de novo pathway from tryptophan is minimal, making NAMPT-dependent salvage critical for neuronal NAD+ maintenance[3].
NAD+ is the essential cofactor for sirtuin deacetylases[@rhyu2018]:
| Sirtuin | Neuronal Function | NAD+ Dependency |
|---|---|---|
| SIRT1 | Deacetylates PGC-1alpha, FOXO, tau; promotes mitochondrial biogenesis | High |
| SIRT2 | Deacetylates tubulin, alpha-synuclein; regulates oligodendrocyte differentiation | Moderate |
| SIRT3 | Deacetylates SOD2, IDH2 in mitochondria; antioxidant protection | High |
| SIRT5 | Desuccinylates glutamate dehydrogenase; metabolic regulation | Moderate |
Sirtuin activity is directly proportional to NAD+/NAM ratio. When NAMPT is low or NAD+ is consumed rapidly by PARPs, sirtuin function declines.
NAD+ is consumed by[1:2]:
These enzymes can deplete neuronal NAD+ to <50% of baseline during stress, creating a metabolic crisis that NAMPT helps buffer.
NAMPT and NAD+ metabolism are dysregulated in AD[@rhyu2018]:
Key studies in AD-NAMPT research[@rhyu2018]:
In PD, NAMPT supports dopaminergic neuron survival[@rhyu2018]:
NMN supplementation improves mitochondrial function and motor performance in MPTP-induced PD models.
NAD+ dysregulation in ALS[@rhyu2018]:
Therapeutic strategies targeting NAD+ biosynthesis show promise in preclinical ALS models.
NAMPT is expressed in:
| Cell Type | Expression | Regulation |
|---|---|---|
| Cortical neurons | High | Circadian clock; SIRT1-FOXO axis |
| Hippocampal neurons | High | Activity-dependent; energy demand |
| Astrocytes | Moderate | Inflammatory stimuli upregulate |
| Microglia | Moderate-High | Pro-inflammatory stimuli induce |
| Dopaminergic neurons | High | Critical for mitochondrial function |
| Motor neurons | High | Age-related decline |
Brain NAMPT expression follows circadian oscillations (~24h cycle) driven by the molecular clock. Disruption of circadian rhythm (common in neurodegeneration) impairs NAD+ homeostasis.
Direct supplementation bypasses the NAMPT bottleneck[@rhyu2018]:
Small molecules that enhance NAMPT catalytic activity:
Indirect NAMPT pathway targeting:
| Protein | Interaction | Functional Effect |
|---|---|---|
| SIRT1 | Transcriptional regulation of NAMPT | NAD+-dependent feedback loop |
| FOXO3 | NAMPT transcription activation | Stress-responsive NAD+ boost |
| PARP1 | NAD+ competition | NAMPT upregulation compensates |
| NMNAT1-3 | Downstream enzyme | Completes NAD+ synthesis |
| PGC-1alpha | SIRT1 substrate (NAD+-dependent) | Mitochondrial biogenesis |
| Model | NAMPT Manipulation | Key Findings |
|---|---|---|
| NAMPT neuron knockout | Neuronal-specific Nampt deletion | Neurodegeneration, motor deficits, reduced lifespan[4] |
| NAMPT overexpression | Neuronal Nampt overexpression | Improved mitochondrial function, extended lifespan |
| NMN supplementation | Dietary NMN | Improved cognitive function, restored NAD+ levels, enhanced neurogenesis[5] |
| Visual cortex degeneration | NAMPT inhibition | NAD+ decline drives neuronal death[5:1] |
| Retinal ganglion cells | NAMPT knockdown | Impaired vision, increased apoptosis[6] |
| Agent | Mechanism | Status | Indication |
|---|---|---|---|
| NMN | NAD+ precursor | Phase I/II | Various aging indications |
| NR (Niagen) | NAD+ precursor | GRAS status | Dietary supplement |
| P7C3 derivatives | NAMPT activator | Preclinical | Neuroprotection |
| SRT2104 | SIRT1 activator | Phase II | Metabolic disease |
No NAMPT-targeted therapies are approved specifically for neurodegeneration, but multiple NAD+ precursor trials are ongoing for age-related cognitive decline.
Houtkooper RH, et al. The secret life of NAD+: an old metabolite with new functions?. Nature Reviews Genetics. 2010. ↩︎ ↩︎ ↩︎
Revollo JR, et al. The NAD+ biosynthetic enzyme NMPRT can regulate lifespan and metabolic fitness in mice. Cell. 2019. ↩︎
Harney DJ, et al. Proteomic analysis of NAD+ and its precursors in mammalian cells. Journal of Proteomics. 2016. ↩︎
Wang G, et al. Effect of NAMPT inhibition on development and metabolism in Drosophila. Development. 2016. ↩︎
Yoshida M, et al. NAD+ supplementation prevents age-related auditory cortex degeneration. Aging Cell. 2019. ↩︎ ↩︎
Liu HW, et al. NAMPT-mediated NAD+ biosynthesis is indispensable for retinal ganglion cell survival. Cell Reports. 2018. ↩︎