Niacin vs. ketosis
Part I. Rodents
It is speculated: niacin binds a particular “ketone” receptor (GPR109?) (physiological relevance?).
It is known: niacin is ketogenic in rats. Repeat: niacin is ketogenic in rats.
Niacin aka nicotinic acid and nicotamide aka niacinamide both fulfill the requirement for Vitamin B3 (ie, prevent pellagra). But only the former causes flushing… and only the former is ketogenic (two apparently unrelated phenomena).