APOC3 and obesity due to melanocortin 4 receptor deficiency: Apo CIII and Apo B100 are important players of lipid metabolism, with 2 (m/z 1716, and 1773 less abundant in obesity) and 3 (m/z 1582, 1796 and 2046 less abundant in obesity) peptides, respectively being dysregulated after MALDI-profiling.