Exercise Boosts NAD+ Enzymes That Drive Longevity and Metabolic Health
A comprehensive review reveals how aerobic and resistance exercise upregulate NAMPT, sirtuins, and other NAD+ enzymes to combat aging.
Summary
This 2026 narrative review synthesizes evidence showing that both aerobic and resistance exercise powerfully modulate NAD+ biosynthesis enzymes—particularly NAMPT and sirtuins—in skeletal muscle and cardiac tissue. Exercise activates the AMPK–NAMPT–NAD+ signaling axis, boosting mitochondrial efficiency, oxidative metabolism, and cellular DNA repair capacity. Notably, older adults appear to gain proportionally larger NAMPT increases from training than younger individuals, suggesting exercise may partially reverse age-related NAD+ decline. While animal and human data are largely supportive, results vary by tissue type, exercise modality, intensity, and measurement method, highlighting the need for standardized protocols in future research.
Detailed Summary
NAD+ is a master coenzyme sitting at the crossroads of cellular energy metabolism, DNA repair, and longevity signaling. Its depletion with age is linked to metabolic dysfunction, neurodegeneration, and reduced healthspan. Understanding how lifestyle interventions—especially exercise—can restore NAD+ levels and enzyme activity is therefore a central question in longevity medicine.
This review, published in Frontiers in Sports and Active Living (2026), conducted a comprehensive narrative synthesis of peer-reviewed literature from 2000–2024 across PubMed, Scopus, Web of Science, and Google Scholar. The authors focused on how aerobic and resistance exercise modulate enzymes in the NAD+ salvage pathway (primarily NAMPT, NMNATs, NRK1/2), biosynthesis pathways (de novo via tryptophan, Preiss–Handler via nicotinic acid), and downstream NAD+-consuming enzymes including sirtuins (SIRT1, SIRT3), PARPs, and CD38.
Key findings center on NAMPT, the rate-limiting enzyme in the salvage pathway. Human studies show aerobic training increases skeletal muscle NAMPT by 12–28% depending on age group, while resistance training produces 25–30% increases, with older adults (>55) showing larger relative gains than younger adults (<35). Endurance-trained athletes show roughly double the skeletal muscle NAMPT protein expression compared to sedentary individuals. Three weeks of exercise training in sedentary non-obese participants produced a striking 127% rise in NAMPT protein, correlated with mitochondrial content. Animal studies confirm that muscle-specific NAMPT overexpression triples voluntary exercise tolerance in mice and dramatically upregulates mitochondrial gene expression. The mechanistic backbone appears to be the AMPK–NAMPT–NAD+ axis: exercise shifts the AMP/ATP ratio, activating AMPK, which drives NAMPT expression and thereby increases NAD+ biosynthesis and mitochondrial adaptation.
Beyond NAMPT, exercise also upregulates sirtuins—NAD+-dependent deacylases that regulate mitochondrial biogenesis (SIRT1/PGC-1α axis), oxidative stress defense (SIRT3), and metabolic flexibility. In Drosophila models, climbing exercise increased cardiac NMNAT expression and NAD+ levels, activating Sir2/FOXO/SOD pathways to protect against cardiac aging and lipotoxic cardiomyopathy. In humans, acute moderate-intensity cycling released NAMPT via extracellular vesicles (EV-eNAMPT), elevating NAD+ in recipient cells—an effect that was more pronounced in younger, fitter individuals.
Importantly, results are not uniform. NAMPT levels in subcutaneous adipose tissue did not change after 6 weeks of HIIT in either young or older adults. Sprint interval training had no effect on plasma NAMPT. NMNAT1/2 showed only modest responses to aerobic and strength training in human skeletal muscle. These discrepancies likely reflect tissue-specific metabolic demands, exercise type, duration, intensity, timing of sample collection, and the specific metric measured (mRNA vs. protein vs. enzymatic activity). The review acknowledges that precise molecular pathways remain incompletely characterized.
Key Findings
- Resistance training raised skeletal muscle NAMPT by ~25–30%; older adults showed larger relative gains than younger individuals.
- Three weeks of exercise in sedentary adults produced a 127% increase in NAMPT protein, correlated with mitochondrial content.
- Acute cycling released EV-eNAMPT into circulation, raising NAD+ in recipient cells and potentially countering age-related NAD+ decline.
- Exercise activates the AMPK–NAMPT–NAD+ axis, linking energy sensing to mitochondrial biogenesis and oxidative metabolism.
- Muscle-specific NAMPT overexpression in mice tripled voluntary exercise endurance and significantly upregulated mitochondrial gene expression.
Methodology
This is a narrative review synthesizing peer-reviewed human and animal studies published from 2000–2024, identified via PubMed, Scopus, Web of Science, and Google Scholar. Studies were included if they examined exercise interventions in relation to NAD+ metabolism, NAD+-dependent enzymes, mitochondrial function, or metabolic health. No meta-analysis or systematic pooling of effect sizes was performed.
Study Limitations
As a narrative review, it is susceptible to selection bias and does not quantitatively pool effect sizes across studies. Significant heterogeneity exists across studies in exercise type, intensity, duration, tissue sampled, and molecular readout, making direct comparisons difficult. Several key findings derive from animal or Drosophila models, and the precise molecular pathways by which exercise modulates NAD+ enzymes in humans remain incompletely characterized.
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