How is NMN metabolized in the human body?

NMN is the abbreviation of Nicotinamide mononucleotide, with a molecular weight of 334.2192. It is an inherent substance in the human body and is also rich in some fruits and vegetables.
In the human body, NMN is the precursor of NAD+, and its function is reflected by NAD+.

NAD+ is also called coenzyme Ⅰ, its full name is nicotinamide adenine dinucleotide, also known as nicotinic acid diphosphate, it exists in every cell and participates in thousands of reactions.
NAD+ is an important coenzyme of the tricarboxylic acid cycle, which promotes the metabolism of sugar, fat, and amino acids, and participates in the synthesis of energy;
NAD+ is the only substrate of coenzyme I consuming enzymes (the only substrate of DNA repair enzyme PARP, the only substrate of long-lived protein Sirtuins, and the only substrate of cyclic ADP ribose synthase CD38/157).

The tricarboxylic acid cycle is the final metabolic pathway of the three major nutrients (sugars, lipids, and amino acids) in the human body, and it is also the hub of the metabolic connection of sugars, lipids, and amino acids. The tricarboxylic acid cycle provides more than 95% of the energy in the body. It is the energy hub of the living body.

NMN is a substance inherent in the human body, and some fruits and vegetables are also rich in.

According to the FDA's equivalence principle, a 70Kg adult should be supplemented with 600mg of NMN per day. To supplement the same amount of NMN, an adult needs to eat 32~128kg of edamame or 54~240kg of broccoli. And this is still in the case of ensuring complete absorption, which is obviously unrealistic, and it is particularly important to supplement NMN from non-food sources.

NAD+ was discovered and named as early as 1904, and its function has been continuously discovered. The research on NAD+ gave birth to six Nobel Prize winners, so NAD+ is also called Noga factor.

NMN is the precursor of NAD+, and its function is also reflected by NAD+. The metabolism of NNM and NAD+ are linked together.
There are three independent metabolic pathways for NAD+ in the human body: Preiss-Handler pathway, de novo synthesis pathway and salvage synthesis pathway.

● Preiss-Handler approach
It was discovered by Preiss and Hsndler in 1957~1958, so it was named Preiss-Handler pathway.
This pathway starts from niacin, which is catalyzed by nicotinic acid phosphoribosyltransferase (NAPRT) to become nicotinic acid mononucleotide, which is catalyzed by NMNATI1~3 enzymes to become nicotinic acid adenine dinucleotide, and then Catalyzed into NAD+.
● De novo synthesis pathway
This pathway is also called the kynurenine pathway.
Starting from tryptophan ingested in food, it turns into quinolinic acid after passing through N-formylkynurenine, L-kynurenine, 5-hydroxy-2-aminobenzoic acid, ACMS, and then quinolinic acid Enter the Preiss-Handler pathway.
The IDO and TDO pathways of tryptophan to N-formylkynurenine are the limiting steps of the de novo synthesis pathway, and ACMS can also enter the tricarboxylic acid cycle.
● Remedial Synthetic Pathways
NAD+ goes through three consumption pathways (sirtuins, PARPs, and the cADPR) and then turns into nicotinamide, and then becomes NMN after being catalyzed by NAMPT, and NMN is also converted into NAD+ through the catalysis of NMNAT1~3 enzymes to complete the cycle.
Studies have shown that the NAD+ produced by the salvage synthesis pathway accounts for 85% of the total NAD+ in the human body, and the NAMPT enzyme in the salvage synthesis pathway is the limiting step of this cycle. The content of NAD+ maintains a balance under these three independent pathways, and the remedial synthesis pathway is the main source of NAD+ in the human body. NAD+ will be repeatedly synthesized 2 to 4 times in a 75kg adult to reach a level of 3g.