Nicotinamide Mononucleotide (NMN) Research

This is the first randomized controlled trial in humans to test whether oral nicotinamide mononucleotide (NMN) — a precursor the body uses to make NAD⁺ — affects how the body handles insulin. Twenty-five postmenopausal women with prediabetes who were overweight or obese took either 250 mg of NMN daily or an identical placebo for 10 weeks. Neither the participants nor the researchers knew which pill each person received until the trial ended.

After 10 weeks, women taking NMN showed a 25% improvement in how effectively their muscles took up glucose in response to insulin, measured with a hyperinsulinemic-euglycemic clamp — the reference method for assessing insulin sensitivity. Women taking placebo showed no such change. Muscle biopsies confirmed that the insulin-signaling machinery inside the muscle cells (the AKT and mTOR pathways) was working harder after NMN. Gene expression analysis showed that NMN activated hundreds of genes involved in muscle repair and remodeling, including the PDGF signaling pathway.

The improvement was specific to muscle. NMN did not change body weight, body fat, liver fat, blood pressure, fasting glucose, fasting insulin, cholesterol, or how insulin acted on the liver or fat tissue. Muscle strength and endurance did not improve during the 10-week window. NMN was well tolerated, with no adverse events reported and standard blood tests unchanged.

This is a two-page perspective article, not a research study. Christopher Shade, PhD — founder and CEO of Quicksilver Scientific, a supplement company that markets a liposomal NMN product — walks a clinician audience through why nicotinamide mononucleotide (NMN) has drawn interest as an anti-aging molecule. The framing is that NAD+, a coenzyme essential for cellular repair and energy production, declines with age, and that NMN supplementation may raise NAD+ levels and produce downstream healthspan benefits.

The article opens with the World Health Organization's 2018 addition of aging to the International Classification of Diseases and uses that framing to argue for pharmacological approaches to age-related decline. It then summarises the enzymatic pathways connecting nicotinamide (vitamin B3) to NAD+ via NMN, describes the roles of the NAMPT enzyme and the Slc12a8 transporter, and reviews reported effects of NMN in mouse studies — including improved insulin sensitivity, improved mitochondrial function, cardiovascular protection, cognitive protection, and preservation of skeletal muscle.

The closing section discusses the then-early state of human research on NMN and speculates that liposomal delivery may enhance NMN uptake — a claim aligned with the author's commercial product. The article contains no original data. It is a synthesis piece intended to introduce the NMN literature to clinicians rather than to add to it.

This 2015 primary research paper reports a finding that runs counter to the simple "more NMN is better" framing common in the supplement space: after nerve injury, NMN itself accumulates inside axons and actively promotes their degeneration. The paper was published in Cell Death and Differentiation, a peer-reviewed Nature Publishing Group journal, by a multi-institutional team led by groups at the University of Nottingham and the Babraham Institute (Cambridge, UK), with collaborators in Italy and the United States.

The background biology: axons depend on an enzyme called NMNAT2 to convert NMN into NAD+. NMNAT2 is a labile protein that has to be continuously delivered from the cell body down the axon. When an axon is cut, or when NMNAT2 is otherwise depleted, this delivery stops. NAMPT — the enzyme upstream of NMNAT2, which makes NMN from nicotinamide — is far more stable and keeps producing NMN. The result: NMN builds up in the injured axon with nowhere to go, because the enzyme that would convert it to NAD+ is gone.

Using three independent methods — the NAMPT inhibitor FK866, which blocks NMN synthesis; a bacterial NMN deamidase enzyme that scavenges NMN; and the well-established WldS protein — the authors show that preventing this NMN rise protects injured axons and their neuromuscular synapses from degeneration. Conversely, adding exogenous NMN reverses that protection. In injured mouse sciatic nerve in vivo, NMN begins rising within 12 hours of injury and reaches roughly 2.5× normal by 30 hours — approximately 24 hours before axons visibly fragment. The same protective effect of NAMPT inhibition was reproduced in zebrafish larvae in vivo.

The scope of the finding is specific and important to understand precisely. This paper documents a mechanism operating in a defined pathological context: axons that have lost NMNAT2 activity and cannot metabolise NMN. The authors themselves note that in other cellular contexts NMN is cytoprotective, because those cells retain NMNAT to convert NMN to NAD+. The paper's contribution is to identify NMN accumulation as an active driver of a specific type of nerve degeneration (Wallerian and Wallerian-like), and to identify NAMPT as a potential therapeutic target for peripheral neuropathies — including chemotherapy-induced peripheral neuropathy, which is the paper's proposed translational application.