NEFL and neuropathy: The markers of DPN assessed in this study were the neuropathy disability score (NDS) and the neuropathy symptom score (NSS), the nerve conduction studies (NCS), the quantitative sensory testing (QST), the assay of circulating biomarkers of DPN, such as the neurofilament light chain protein (NFL), and the detection of structural nerve damage by magnetic resonance neurography (MRN).