LEP and obesity due to melanocortin 4 receptor deficiency: Established and novel obesity-related biomarkers include those of glucose-insulin homeostases such as insulin, proinsulin, C-peptide, and insulin-like growth factors; biomarkers of adipose tissue such as leptin, resistin, apelin, adiponectin, omentin, and fatty-acid-binding protein-4; inflammatory biomarkers such as CRP, TNF-α, IL-6, and omics-based biomarkers such as microRNAs and metabolites [61].