The liver's role in maintaining NAD+ reserves and controlling nicotinamide release to other tissues is analogous to how the liver manages blood glucose levels.

“so in that sense it's actually sort of parallels glucose right in the sense that we have to we have to maintain about Foxley grams of glucose in our bloodstream at all times so if you have 10 grams of glucose in your bloodstream you have diabetes you've got huge problems you're gonna go blind and get your toes cut not if you have 100 grams in your liver exactly but 5 grams is perfect and if by the way if you have 2 grams you die you know it's just it's an amazing problem where the liver is constantly titrating so you're basically drawing a parallel that says it's probably doing the same thing holding on to nad”