Indeed, a linkage study of an F2 intercross between B6 and DBA/2 mouse lines with a deficiency in the leptin receptor (db/db) identified an interval of chromosome 4 that was associated with the traits blood glucose and plasma triacylglycerols [19], confirming that the region is responsible for obesity-induced diabetes. Here, LEPR is linked to obesity due to melanocortin 4 receptor deficiency.