DLK1 and obesity due to melanocortin 4 receptor deficiency: In obesity, a study not only identified two major adipokine clusters related to either body fat mass and inflammation or insulin sensitivity/hyperglycemia, and lipid metabolism (DLK1, SFRP5, and the like) but also revealed DLK1, Angiopoietin-like protein 6 (ANGPTL6), nicotinamide phosphoribosyl transferase (Nampt), and progranulin as the strongest adipokine correlates of type 2 diabetes (T2D) in obese individuals [23].