APLN and obesity due to melanocortin 4 receptor deficiency: We also observed that obese patients with type 2 DM had significantly higher apelin levels than non-diabetic obese subject (1.62±1.43 ng/mL vs 0.97±0.78 ng/mL, P = 0.015) confirming that increased apelin levels are directly associated with the presence of diabetes rather than obesity itself.