NAD+

Nicotinamide adenine dinucleotide, NAD+ for short, is not a peptide but a coenzyme found in every living cell and involved in a wide range of metabolic steps. It became interesting for aging research because the cellular supply shrinks markedly over the years, and with it the capacity of key repair systems.

Three mechanisms stand out in the literature:

• Sirtuins: These deacetylases work only with NAD+ as a partner. They govern metabolism, DNA repair, mitochondrial function and the response to cellular stress. As NAD+ runs low they lose activity, which preclinical work links to accelerated cellular aging.
• Consumption by PARP and CD38: The PARP family of DNA repair enzymes and the enzyme CD38 draw on the pool as well, amplifying the age-related decline.
• Sirt1/AMPK/PGC-1α: When the level is lifted again in animal models via precursors such as NMN or NR, this axis switches on. Observed were better mitochondrial function, less oxidative stress, less inflammation and fewer senescent cells.

In roundworms (C. elegans) the mitochondrial stress response UPRmt and FOXO signaling are additionally tied to a longer lifespan. While many studies work with precursors, part of the field applies the coenzyme directly, often in larger amounts than are usual for NMN or NR. How well it becomes available after subcutaneous or intramuscular dosing is currently being examined in preclinical models. The material arrives as a freeze-dried powder that is dissolved in bacteriostatic water before use; the concentration follows from the volume added.

As an endogenous molecule, NAD+ is thoroughly familiar. The safety topic lies elsewhere: with parenteral dosing of larger amounts, the literature describes a reaction pattern that depends above all on the pace of administration.

• Given too fast: Reports mention intense flushing, a pressure on the chest, nausea and inner restlessness. When the pace is slowed, these reactions usually fade.
• Circulation: Short-lived swings in pulse and perceived warmth during dosing are reported regularly.
• Injection site: With large amounts per dose, irritation of the injection site is common.
• Data situation: Robust human studies on prolonged, high-dose parenteral use do not exist. What is known comes from animal models, from precursor studies and from experience reports.

This summary is no substitute for medical advice.

• It takes two to tango: NAD+ and sirtuins in aging/longevity control - review by Imai and Guarente that organizes the interplay of NAD+ and sirtuins in aging.
• The NAD+/sirtuin pathway modulates longevity through mitochondrial UPR and FOXO signaling - shows how this pathway influences lifespan through the mitochondrial stress response and FOXO.
• NAD+ and Sirtuins in Aging and Disease - summarizes the coenzyme's role in aging processes and disease mechanisms.