Beta-NMN

In the salvage pathway, β-nicotinamide mononucleotide (NMN) is synthesized from NAM and PRPP by NAMPT-the rate-limiting enzyme for mammalian NAD+ biosynthesis-or from NR via NRK-mediated phosphorylation; NMN is subsequently converted into NAD+ by NMNATs. In mammals, there are three NMNAT isoforms encoded by distinct genes-NMNAT1, NMNAT2, and NMNAT3-localized in the nucleus, Golgi apparatus, and mitochondria, respectively. Enzymes that consume NAD+ within the salvage pathway (such as PARPs, Sirtuins, CD38/T10, CD157/BST1, and SARM1) degrade NAD+ while performing their enzymatic functions, generating NAM as a byproduct; NAM is then methylated by NNMT to form MeNAM, which is further broken down into Me2PY and Me4PY for excretion. NAMPT is the rate-limiting enzyme of the salvage pathway; total NAMPT deficiency in mice results in embryonic lethality. Furthermore, tissue-specific deletion of NAMPT in mouse tissues-including skeletal muscle, liver, and adipose tissue-reduces NAD+ levels in the respective organs.

In addition to the primary salvage pathway, NAPRT catalyzes a step in the Preiss-Handler pathway, converting NA into NAMN; meanwhile, the *de novo* pathway converts Trp into QA, which is then transformed into NAMN via QPRT catalysis, marking the convergence of these two pathways. Following a series of reactions that convert the intermediates into NAAD, the process culminates in the formation of NAD+ via the action of NADS.

Regarding the uptake and utilization of β-nicotinamide mononucleotide (β-NMN), studies using stable isotope-labeled NMN have revealed that NMN is dephosphorylated extracellularly into nicotinamide riboside (NR); research employing various chemical inhibitors indicates that NR enters cells via equilibrative nucleoside transporters (ENTs). However, NR is unstable and rapidly degrades into nicotinamide (NAM) in mouse plasma or culture media containing fetal bovine serum. This suggests that after oral administration and entry into the bloodstream, β-NMN can be extracellularly converted into NR and subsequently transported into cells, although a portion is converted into NAM-either through hepatic metabolism or hydrolysis within the circulation-following its conversion to NR.

Based on recent preclinical and clinical studies, research applications for Beta-NMN focus on the following key domains:

Anti-Aging & Mitochondrial Protection

Mitochondrial Biogenesis: Elevates the NAD+/NADH ratio, restoring mitochondrial respiratory chain activity and ATP production in senescent cells.

Physical Function Enhancement: Clinical trials demonstrate that Beta-NMN supplementation improves muscle strength, walking speed, and endurance in middle-aged and older adults.

Metabolic Health & Insulin Sensitivity

Glucose & Lipid Metabolism: Studies show Beta-NMN significantly alleviates insulin resistance induced by high-fat diets or aging, boosting glucose utilization in the liver and skeletal muscle.

Weight Management: Promotes fatty acid β-oxidation, assisting in energy expenditure balance.

Cardiovascular & Neuroprotective Effects

Endothelial Function Restoration: Activates SIRT1 to promote endothelial nitric oxide synthase (eNOS) expression, improving vascular elasticity and microcirculation.

Neurodegenerative Research: Increases brain NAD+ levels, reducing neuroinflammation, amyloid-beta (Aβ) deposition, and neuronal apoptosis in Alzheimer's disease models.

DNA Repair & Stress Resistance

Enhances cellular self-repair capabilities against ultraviolet (UV) radiation, ionizing radiation, or chemical toxins, maintaining genomic stability.