APLN and diabetes mellitus: Moreover, lipoic acid has reported beneficial effects in the treatment of diabetes complications.[34] Additionally, methylcobalamin could promote myelinogenesis and axon regeneration through nucleic acid and protein synthesis, repairing peripheral nerve injury.[35,36] Our study showed that the serum apelin level was closely associated with DPN and its expression was decreased after lipoic acid and methylcobalamin, thus preventing the progression of neuropathy.