Mechanism summary
NAD+ Decline in Aging: Sirtuin, PARP, and Mitochondrial Mechanisms — VialBase Research
NAD+ declines ~50% between ages 40-60 in humans
Last updated · 2018-2025 · Compiled from Rajman et al. 2018, Yoshino et al. 2018, and others · Cell Metab and various
Key findings
- NAD+ declines ~50% between ages 40-60 in humans
- Sirtuins (SIRT1-7) require NAD+ as obligate substrate
- PARP1 DNA repair competes with sirtuins for NAD+ pool
- CD38 (NADase) increases with aging and is major NAD+ consumer
- NMN and NR oral supplementation raises blood NAD+ 40-90%
- Multiple human RCTs support NAD+ boosting for metabolic health
NAD+ Decline in Aging: Core Mechanisms
The NAD+ Decline
- NAD+ levels decline approximately 50% between ages 40 and 60
- Primary drivers: increased CD38 (NADase) expression, increased PARP activity from accumulated DNA damage, decreased NAMPT (salvage pathway enzyme)
- Consequence: insufficient substrate for sirtuins, PARPs, and mitochondrial function
Sirtuin Dependency
- SIRT1 (nuclear): gene silencing, metabolic adaptation, stress resistance
- SIRT3 (mitochondrial): fatty acid oxidation, ROS detoxification, electron transport
- SIRT6 (nuclear): DNA repair, telomere maintenance, glucose homeostasis
- All require NAD+ as obligate co-substrate; activity declines proportionally with NAD+
Competition Model
- PARP1 consumes 80-90% of cellular NAD+ during DNA damage response
- CD38 expression increases 2-3x with aging, consuming NAD+ constitutively
- This leaves insufficient NAD+ for sirtuin activation
- NAD+ supplementation restores the balance
Supplementation Strategies
| Strategy | Route | Evidence Level |
|---|---|---|
| NMN | Oral | Multiple human RCTs; raises NAD+ 40-60% |
| NR (Niagen) | Oral | Multiple human RCTs; raises NAD+ 40-90% |
| NAD+ IV | Intravenous | Clinical use; limited RCTs |
| NAD+ SubQ | Subcutaneous | Growing clinical use |
| Niacin | Oral | Oldest form; flushing side effect |
Relevance
Provides the foundational rationale for NAD+ supplementation in anti-aging protocols. The sirtuin-PARP competition model explains why simply activating sirtuins (e.g., with resveratrol) is insufficient without adequate NAD+ substrate.