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NMN and the hallmarks
of aging — mapping
where the biology connects.
Aging biology has a framework — a set of cellular and molecular features, first formally described in 2013 and since expanded, that characterize what happens to cells as organisms age. Mapping where NAD+ biology and NMN fit within that framework is the clearest way to understand both what the NMN story is about and what it is not about. Not every hallmark connects. The ones that do connect substantively. The distinction matters.
I
The biological map of aging —
and why it matters for understanding NMN.
In 2013, a landmark paper in Cell by Carlos López-Otín and colleagues introduced a conceptual framework that has since become foundational in aging biology: the hallmarks of aging. The framework identified nine cellular and molecular features that, taken together, characterize the biological process of aging across species — features that are universal, progressive, and causally connected to the deterioration in cellular function that defines getting older. A 2023 update to the framework expanded the hallmarks to twelve, incorporating new findings from the decade of research that followed.
The hallmarks are not a list of symptoms. They are a mechanistic map — a description of what is actually happening inside cells as they age, at the level of molecular biology. Genomic instability. Telomere attrition. Epigenetic alterations. Loss of proteostasis. Disabled macroautophagy. Deregulated nutrient sensing. Mitochondrial dysfunction. Cellular senescence. Stem cell exhaustion. Altered intercellular communication. Chronic inflammation. Dysbiosis. Each hallmark names a specific biological process that deteriorates with age and that contributes to the aging phenotype at the cellular and organismal level.
NAD+ biology — and by extension, NMN as its most direct precursor — does not appear in every hallmark. The connections are concentrated, not universal. But where they do appear, they appear at the mechanistic core of the hallmark rather than at its periphery. Understanding which hallmarks connect to NAD+/NMN biology, how directly, and through which mechanisms is the purpose of this article. It is also the most honest and intellectually rigorous way to position what NMN is — and what it is not — in the broader landscape of aging science.
Not every hallmark of aging
connects to NAD+ biology.
The ones that do connect
at the mechanistic core —
not at the periphery.
The Twelve Hallmarks — Mapped
Every hallmark of aging —
and where NAD+/NMN biology connects.
Connection levels reflect the documented mechanistic relationship between NAD+ biology and each hallmark in the current literature — not product claims. The framework is still evolving, and connections continue to be characterized.
II
The five hallmarks where
the NAD+/NMN connection is most direct.
Of the twelve hallmarks, five have documented mechanistic connections to NAD+ biology that run through the core of the hallmark rather than its edges: genomic instability, telomere attrition, epigenetic alterations, deregulated nutrient sensing, and mitochondrial dysfunction. These are not all equally well-characterized, and the depth of the NAD+ connection differs across them — but in each case, the mechanism is specific, documented, and integrated into how the field thinks about that hallmark.
What is notable about this set is its coherence. These five hallmarks are not randomly distributed across the aging landscape. They are concentrated in the cellular maintenance and regulatory systems — the systems responsible for keeping the genome intact, maintaining gene expression patterns, managing energy metabolism, and responding to nutrient signals. These are exactly the systems that sirtuins govern, that PARP enzymes operate within, and that the mitochondrial NAD+ pool supports. The NAD+/NMN axis does not touch aging everywhere — but it touches it in the systems that are most central to how cellular integrity is maintained across time.
The Direct Connections
Five hallmarks — and how NAD+
biology connects to each one.
DNA repair is NAD+-dependent — and its demand grows as damage accumulates with age
The connection between genomic instability and NAD+ runs through PARP biology: PARP1 and PARP2 detect DNA strand breaks and consume NAD+ to synthesize the PAR scaffolds that recruit repair machinery. As damage accumulates with age and PARP activation becomes more frequent, the NAD+ demand of the repair response grows — drawing on a pool that declining NAMPT is simultaneously making smaller. SIRT1 and SIRT6 add further connection through their roles in chromatin regulation at DNA damage sites and telomeres. The genomic instability hallmark is one of the two most mechanistically direct connections to NAD+ biology in the entire framework.
Sirtuin-mediated histone deacetylation is a primary mechanism of epigenetic maintenance — and it requires NAD+
The epigenetic alterations that accumulate with age — progressive loss of histone modifications, drift in DNA methylation patterns, dysregulation of gene expression — are partly maintained against by sirtuin activity. SIRT1 deacetylates H3K9ac and H4K16ac, modifications whose maintenance is associated with heterochromatin stability. SIRT6 specifically deacetylates H3K9ac and H3K56ac at telomeric chromatin and DNA damage sites. SIRT7 targets H3K18ac to regulate stress response genes. All three depend on NAD+, placing the epigenetic maintenance function of the sirtuin family in direct relationship with the NAD+ availability that aging progressively reduces.
Sirtuins are nutrient sensors — they couple NAD+ availability to metabolic gene regulation
The deregulated nutrient sensing hallmark covers the age-related dysfunction of signaling pathways — mTOR, AMPK, insulin/IGF-1, and sirtuins — that govern how cells respond to nutrient availability. Sirtuins are specifically listed in the hallmark framework as one of the four major nutrient-sensing axes, alongside mTOR, AMPK, and insulin/IGF-1. They function as metabolic sensors because their activity is directly coupled to NAD+ — the redox currency that reflects cellular energy status. When NAD+ declines with age, sirtuin-mediated metabolic sensing is attenuated, contributing directly to the nutrient sensing deregulation that the hallmark describes.
Three of the seven sirtuins live inside mitochondria — and the mitochondrial NAD+ pool governs all of them
The mitochondrial dysfunction hallmark has one of the most extensive and well-characterized connections to NAD+ biology in the entire framework. Three sirtuins — SIRT3, SIRT4, and SIRT5 — reside in the mitochondrial matrix and depend on the mitochondrial NAD+ pool (maintained by NMNAT3, distinct from nuclear and cytoplasmic pools). SIRT3 alone has more than 100 documented mitochondrial protein substrates. The NAD+/NADH ratio that governs electron transport chain efficiency, the PGC-1α axis that governs mitochondrial biogenesis, and the mitophagy coordination that maintains network quality all intersect with NAD+ availability in ways that the mitochondria article in this series covers in full.
SIRT6 specifically localizes to telomeres — and its activity there depends on nuclear NAD+ availability
Telomere attrition — the progressive shortening and dysfunction of telomeres with each cell division — is connected to NAD+ biology primarily through SIRT6. SIRT6 deacetylates H3K9ac specifically at telomeric chromatin, a modification associated with telomere stability and protection. SIRT1 also contributes through its regulation of the transcription of TERRA (telomeric repeat-containing RNA), which has roles in telomere maintenance. Both enzymes draw on the nuclear NAD+ pool, meaning that the telomere protection function of this sirtuin pair is directly subject to the NAD+ decline that aging drives through the nuclear compartment.
The Framework in Numbers
What the hallmarks mapping
shows in structural terms.
12
Hallmarks of aging in the 2023 framework — expanded from the original nine identified in 2013
The hallmarks framework has expanded as aging biology has developed — from nine hallmarks in the original 2013 Cell paper to twelve in the 2023 update, incorporating disabled macroautophagy, chronic inflammation, and dysbiosis as additional features. The framework itself continues to evolve as new findings refine our understanding of which cellular processes are causal versus consequential in the aging process, and how the hallmarks interact with each other.
5
Hallmarks with direct mechanistic connections to NAD+/sirtuin/PARP biology in the current literature
Five of the twelve hallmarks — genomic instability, telomere attrition, epigenetic alterations, deregulated nutrient sensing, and mitochondrial dysfunction — have documented direct connections to the NAD+/sirtuin/PARP axis. Three more have peripheral connections. One has no established connection. This distribution reflects the concentrated but genuine scope of NAD+ biology in the aging landscape — broad enough to be systemically significant, specific enough to be mechanistically meaningful.
1
Molecular axis — NAD+/NMN/sirtuin/PARP — that spans five hallmarks simultaneously
What makes the NAD+ axis unusual in the hallmarks framework is that a single molecular biology story — NAD+ decline, driven by NAMPT reduction and CD38 elevation, constraining sirtuin activity and PARP response capacity — connects to five distinct hallmarks through coherent mechanistic pathways. Most molecular interventions in aging biology touch one or two hallmarks. The sirtuin–NAD+–NMN axis touches five through a single connected story. That coherence is part of what has made it one of the most intensively studied areas in contemporary longevity science.
III
What mapping NMN to the hallmarks
actually tells us.
The exercise of mapping NMN biology to the hallmarks of aging framework is useful precisely because it is honest in both directions. It shows where the connections are real and mechanistically grounded — and it shows where they are not, or where they are peripheral enough to be characterized as emerging rather than established. That honesty is itself a form of scientific authority: the claim that NAD+/NMN biology is relevant to five of twelve aging hallmarks through specific, documented mechanisms is a stronger position than a vaguer claim about aging in general.
It also places NMN in its proper biological context. The five hallmarks where the connection is direct — genomic instability, telomere attrition, epigenetic alterations, nutrient sensing, and mitochondrial dysfunction — are among the most mechanistically central in the entire framework. They are the hallmarks that govern cellular maintenance at the most fundamental level: how DNA is protected, how gene expression is regulated, how energy is produced, how nutrients are sensed and responded to. The NAD+ axis does not touch aging at its surface. It touches the systems that determine how well the cell can maintain itself across time — which is precisely the framing that the Codeage approach to Cellular Longevity is built around. The hallmarks framework, like all frameworks in biology, continues to be refined as new evidence accumulates — and the connections described here reflect current understanding rather than a final account.
For the detailed biology behind each of the direct connections described here, the series articles on sirtuins, mitochondria, and DNA repair each cover one hallmark connection in full mechanistic depth.
The NAD+ axis does not touch
aging at its surface.
It touches the systems that determine
how well the cell can maintain
itself across time.
Codeage · Pillar 03 · Cellular Longevity
Built for the
cellular long game.
Cellular Longevity is Pillar 03 of The Longevity Code — the dimension of the system built around NAD+ biology, mitochondrial health, and the science of cellular aging.
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