LEPR and obesity due to melanocortin 4 receptor deficiency: Indeed, a higher expression of akr1b1 was only observed in liver tissues of STZ-induced type 1 diabetic mice on 4-week period [51], though increased flux of polyol pathway was not detected using microarray analysis in the liver tissues of ZDF rats which are characterized by obesity and type 2 diabetes with a point mutation in the leptin receptor [9, 10].