Does anyone know how to source, try?
[some people have deficits in NAMPT pathway]
3. NRH (dihydronicotinamide riboside) — the genuinely different one
This is the most interesting precursor most people haven’t heard of. NRH is the reduced form of NR and uses a completely separate fifth pathway to NAD+ synthesis — goes through adenosine kinase rather than NRK. A comparison study showed that unlike NMN, NR, or nicotinamide, only NRH markedly increased NAD+ in macrophages, including a human monocytic cell line. nihSciexplor
The weird wrinkle: extreme NAD+ boosting via NRH induces cytotoxicity in some cellular contexts — the molecule is very potent, which cuts both ways. No human trials yet I can find, but the mechanistic differentiation from existing precursors is real. This is the one to watch.
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What Brenner himself has been doing beyond “just NR”
NAR (nicotinic acid riboside) — the quiet one
This is genuinely Brenner-adjacent and very recent. Brenner wrote a commentary in Cell Metabolism in July 2025 specifically on nicotinic acid riboside (NAR), flagging it as one of the two nucleoside NAD precursors and arguing it functions in systemic NAD homeostasis in a way previously underappreciated. PubMed
The underlying paper that prompted this is striking: researchers knocked out NMNAT1 specifically in liver and found the liver massively accumulated NAR, identified NT5C2 as the enzyme making it, and found the liver releases NAR into circulation while kidneys take it up via NRK1 to synthesize NAD+ — so there’s a whole liver-kidney axis using NAR as a shuttle that nobody knew about. NAR supplementation apparently ameliorated aging-associated NAD+ decline and kidney dysfunction in mice. Cell PressScienceDirect
NAR differs from NR in that it goes through the deamidated (Preiss-Handler) pathway rather than the amidated salvage pathway — so it hits different tissues with a different metabolic signature. No human trials yet that I can find, but Brenner is clearly watching this closely. The fact that he wrote a commentary specifically elevating this work is a signal.