Nicotinamide (NAM) levels are modulated by the action of three enzymes involved in nicotinamide salvaging. They are nicotinamide deaminase, nicotinamide phosphoribosyltransferase and nicotinate phosphoribosyltransferase. These enzymes are poorly characterized in humans, depsite their importance in NAM utilization (Magni et al. 2004). Although not a salvage reaction, NAM levels can also be regulated by nicotinamide N-methyltransferase (NNMT), a potential regulator of diet-induced obesity (Kraus et al. 2014).