Over the past decade, AT has been proposed as an endocrine organ that secretes bioactive peptides, termed ‘adipocytokines’ and has been identified as potential link between obesity and other metabolic disease states, including irisin, which works through autocrine, paracrine, and endocrine effects [26,27,28]. The gene discussed is FNDC5; the disease is obesity due to melanocortin 4 receptor deficiency.