Interestingly, Spite et al. (2011) revealed that BLT1 deletion (BLT1−/− mice) results in the total elimination of monocyte expansion in obesity, indicating that the LTB4/BLT1 pathway is the key regulatory mechanism behind the enhanced expression of monocytes in metabolic disorders. Here, LTB4R is linked to obesity due to melanocortin 4 receptor deficiency.