Consequently, it is very important to systematically analyze whether the association with the risk of metabolic diseases and Mn levels is modified by genetic variation in MnSOD, Cu/ZnSOD, and related genes associated with Mn uptake, transport, metabolism, and excretion, such as DMT1, transferrin receptor (TfR), and soluble carrier family (SLC). The gene discussed is CCL21; the disease is metabolic disease.