Fatty acid-binding protein 4 (FABP4) and neuregulin 4 are another two proteins secreted by adipocytes with relatively opposite functions, since FABP4 was associated with obesity, insulin resistance, type 2 diabetes mellitus, and cardiovascular risk [80], while neuregulin 4 seems to counteract obesity-associated complications like chronic inflammation and metabolic changes in the liver [75,81]. The gene discussed is NRG4; the disease is obesity due to melanocortin 4 receptor deficiency.