Although IL-33 can act as either pro- or anti-inflammatory cytokine, it was shown that administration of recombinant IL-33 in genetically obese diabetic (ob/ob) mice resulted in reduced adiposity, decreased fasting glucose, and improved glucose and insulin tolerance, suggesting a protective role of IL-33 in the development of adipose tissue inflammation during obesity [45]. This evidence concerns the gene INS and obesity due to melanocortin 4 receptor deficiency.