Purwata et al. investigated the role of TNF-α and nitric oxide (NO) in the pathogenesis of painful diabetic neuropathy and found that in the patients with diabetic neuropathy, higher levels of TNF-α and higher inducible NO synthase (iNOS) and TNF-α immunoreactivity of macrophages increased the risk of pain and painful diabetic neuropathy [28]. Here, TNF is linked to diabetic neuropathy.