FABP4 and obesity due to melanocortin 4 receptor deficiency: Irisin is a cytokines and peptide, derived from skeletal muscle, known as a myokine, and exerts either autocrine, paracrine or endocrine effects Adipocyte fatty acid-protein (A-FABP), known as FABP4, and autotaxin (ATX) are secreted by adipose tissues, and have been pointed to be associated with obesity.