KKAy mice (the yellow offspring obtained from a cross of black KK females with obese yellow Ay males) are obese, hyperglycemic, hyperinsulinemic, hypertriglyceridemic, hypercholesterolemic, insulin resistant, and exhibit steatosis with inflammation (steatohepatitis) because of the antagonism between melanocortin receptor 4 (MC4R) and the ectopic expression of the agouti protein [58]. Here, MC4R is linked to steatosis.