Hyperglycemia in diabetes mellitus (DM) can result in increased flux of polyol pathways (in Schwann cells), decreased production of neurotrophic factors (myelin, ciliary neurotrophic factor (CNTF), nerve growth factor (NGF), and neurotrophin-3 (NT-3)), mitochondrial dysfunction, oxidative stress, altered lipid metabolism, the release of inflammatory factors leading to neuroinflammation, axonal demyelination, and a slow nerve conduction velocity (NCV) [28,29]. This evidence concerns the gene NGF and diabetes mellitus.