RARB and type 2 diabetes mellitus: More importantly, we found a nearly 1-fold increase in Rol, a halving of atRA, and significant decreases in retinoic acid receptor α (RARa) and retinoic acid receptor β (RARb) in the hearts of 32-week-old db/db mice (Fig. 1f and g), indicating a retinol metabolism disorder characterized by Rol overload, atRA deficiency, and RARs reduction was present in the hearts of T2DM mice.