NAD, aging, and niacin

A lot of hubbub recently over the announcement that some scientists had managed to make old mice (2 years old) almost like young (6 months). Now they say that there will be a human trial. Here’s the original paper that all the news accounts are based on: Declining NAD+ Induces a Pseudohypoxic State Disrupting Nuclear-Mitochondrial Communication during Aging

Authors
Ana P. Gomes, Nathan L. Price, Alvin J.Y. Ling, Javid J. Moslehi, Magdalene K. Montgomery, Luis Rajman, James P. White, João S. Teodoro, Christiane D. Wrann, Basil P. Hubbard, Evi M. Mercken, Carlos M. Palmeira, Rafael de Cabo, Anabela P. Rolo, Nigel Turner, Eric L. Bell, David A. Sinclair

Highlights
A specific decline in mitochondrially encoded genes occurs during aging in muscle
Nuclear NAD+ levels regulate mitochondrial homeostasis independently of PGC-1α/β
Declining NAD+ during aging causes pseudohypoxia, which disrupts OXPHOS function
Raising nuclear NAD+ in old mice reverses pseudohypoxia and metabolic dysfunction

Summary

Ever since eukaryotes subsumed the bacterial ancestor of mitochondria, the nuclear and mitochondrial genomes have had to closely coordinate their activities, as each encode different subunits of the oxidative phosphorylation (OXPHOS) system. Mitochondrial dysfunction is a hallmark of aging, but its causes are debated. We show that, during aging, there is a specific loss of mitochondrial, but not nuclear, encoded OXPHOS subunits. We trace the cause to an alternate PGC-1α/β-independent pathway of nuclear-mitochondrial communication that is induced by a decline in nuclear NAD+ and the accumulation of HIF-1α under normoxic conditions, with parallels to Warburg reprogramming. Deleting SIRT1 accelerates this process, whereas raising NAD+ levels in old mice restores mitochondrial function to that of a young mouse in a SIRT1-dependent manner. Thus, a pseudohypoxic state that disrupts PGC-1α/β-independent nuclear-mitochondrial communication contributes to the decline in mitochondrial function with age, a process that is apparently reversible.

NAD+ stands for nicotinamide adenine dinucleotide, which is a completely normal biological compound such that giving it is unlikely to cause unwanted side effects. The cell absolutely cannot function without it. The astute reader may perceive that the first word in its name is the same as one of the forms of vitamin B3 – nicotinamide, the other form being nicotinic acid, or niacin. NAD itself is unavailable as a supplement to my knowledge, and you might have to inject it anyway.

But B3 is of course not only available, but safe and cheap. Does it raise levels of NAD+? Why yes, it does. NAD Biosynthesis in Humans – Enzymes, Metabolites and Therapeutic Aspects

NAD plays a major role in all cells as substrate for signal transduction and as cofactor in metabolic redox reactions. Since NAD-dependent signaling involves degradation of the nucleotide, continuous restoration of cellular NAD pools is essential. Moreover, NAD-dependent signaling reactions, which include ADP-ribosylation, protein deacetylation by sirtuins and calcium messenger synthesis, are regulated by NAD availability. Consequently, perturbations of NAD supply can have severe consequences and, in fact, have been associated with major human diseases such as age- and dietinduced disorders, neurodegenerative diseases and cancer. Given the increasing awareness of the biological roles of NAD, the routes, molecular mechanisms and regulation of NAD biosynthesis have been the subject of intense research over the last decade. Impressive progress has been made regarding the molecular identification, functional and structural characterization as well as regulation of the human NAD biosynthetic enzymes. Exciting therapeutic concepts have emerged, which aim at modulation of NAD availability by interfering with the biosynthetic network to prevent, reduce or reverse pathological conditions. Since there are several entry points into NAD synthesis, including the known vitamin B3 precursors nicotinamide and nicotinic acid, targeted nutritional supplementation is likely to have beneficial effects in various diseases. On the other hand, inhibition of NAD synthesis promotes cell death and has emerged as a therapeutic concept for cancer treatment.

Here’s another: Exploring the therapeutic space around NAD+.

Nicotinamide Prevents NAD+ Depletion and Protects Neurons Against Excitotoxicity and Cerebral Ischemia: NAD+ Consumption by SIRT1 may Endanger Energetically Compromised Neurons

Nicotinamide, an NAD+ precursor and an inhibitor of SIRT1 and PARP1, inhibited SIRT1 deacetylase activity without affecting SIRT1 protein levels. NAD+ levels were preserved and PAR accumulation and neuronal death induced by excitotoxic insults were attenuated in nicotinamide-treated cells. Treatment of neurons with the SIRT1 activator resveratrol did not protect them from glutamate/NMDA-induced NAD+ depletion and death. In a mouse model of focal cerebral ischemic stroke, NAD+ levels were decreased in both the contralateral and ipsilateral cortex 6 h after the onset of ischemia. Stroke resulted in dynamic changes of SIRT1 protein and activity levels which varied among brain regions. Administration of nicotinamide (200 mg/kg, i.p.) up to 1 h after the onset of ischemia elevated brain NAD+ levels and reduced ischemic infarct size. Our findings demonstrate that the NAD+ bioenergetic state is critical in determining whether neurons live or die in excitotoxic and ischemic conditions, and suggest a potential therapeutic benefit in stroke of agents that preserve cellular NAD+ levels.

So, vitamin B3, nicotinamide or niacin, may very well be an anti-aging compound.

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