We have previously utilized ZO rats to elucidate the cellular and molecular mechanisms underlying reversal of obesity-associated DD by several therapeutics, including a beta blocker [23], a Dipeptidyl peptidase-4 (DPP-4) inhibitor, and a mineralocorticoid receptor blocker [24, 25]. The gene discussed is DPP4; the disease is obesity due to melanocortin 4 receptor deficiency.