NMN is a nucleotide derived from ribose and nicotinamide. Like nicotinamide riboside, NMN is a derivative of niacin, and humans have enzymes that can use NMN to generate nicotinamide adenine dinucleotide (NADH). In mice, NMN enters cells via the small intestines within 10 minutes converting to NAD+ through the Slc12a8 NMN transporter. Because NADH is a cofactor for processes inside mitochondria, for sirtuins, and for PARP, NMN has been studied in animal models as a potential neuroprotective and anti-aging agent. Dietary supplement companies have aggressively marketed NMN products claiming those benefits. Doses of up to 500 mg was shown safe in men in a recent human study at Keio University School of Medicine, Shinjuku, Tokyo Japan. Multiple long-term human studies are underway.