PON1 and obesity due to melanocortin 4 receptor deficiency: There was a significant decrease in the serum paraoxonase-1 levels in individuals with obesity-associated hyperleptinemia and compared to those participants with a normal weight (3.44 ± 1.08 ng/mL vs. 9.57 ± 2.89 ng/mL, p < 0.001, Figure 2a).