Interestingly, the expression of genes involved in low-grade inflammation associated with obesity such as COX-2 (cyclooxygenase 2), CTSS (cathepsin S), and MMP9 (matrix metalloproteinase-9), which are also AhR target genes, was elevated in obese patients. The gene discussed is MMP9; the disease is obesity due to melanocortin 4 receptor deficiency.