STAC3 and thymus atrophy: NAM also diminished hepatic vacuolization and lipid accumulation by TCDD as shown by Oil Red O staining and triglyceride measurements (Fig. 1k and Supplementary Fig. S4) and the incidence of steatosis (Fig. 1l), supporting a role for NAD+ depletion in steatosis as well as thymus atrophy by TCDD.