Interleukin-6 Levels in Patients With Diabetic Polyneuropathy

Introduction Diabetic polyneuropathy (DPN) is a common chronic complication of type 2 diabetes. The pathogenesis of DPN is still debated, but proinflammatory cytokine mediators like interleukin-6 (IL-6) are possibly involved. We conducted this cross-sectional observational study to assess whether IL-6 levels increase in patients with DPN. Materials and methods This study was conducted at the Institute of Post Graduate Medical Education and Research Hospital in Kolkata, India, from 2016 to 2017. The study included 57 patients aged 30 to 60 years diagnosed with type 2 diabetes with neuropathy on clinical examination and nerve conduction study. Patients with neuropathy due to other causes were excluded. The study participants were assigned into one of four groups. Group 1 (n=15) served as healthy control patients, Group 2 (n=12) contained patients with type 2 diabetes without neuropathy, Group 3 (n=20) contained patients with type 2 diabetes with painful neuropathy, and Group 4 (n=10) contained patients with type 2 diabetes with painless neuropathy. We compared IL-6 levels between each group.  Results There was no significant difference in serum IL-6 levels between healthy controls (Group 1) and patients with type 2 diabetes without neuropathy (Group 2). However, we noted a significant increase in serum IL-6 levels among patients with painful DPN (Group 3) compared to control groups. Interestingly, serum IL-6 levels were higher in patients with painful DPN (Group 3) than patients with painless DPN (Group 4). Conclusions IL-6 increases significantly in painful diabetic neuropathy patients compared to patients with diabetes with painless neuropathy and thus may have a role in the pathogenesis of pain in DPN. Serum IL6 level can be a potential noninvasive marker of painful DPN, and it can help distinguish painful DPN from other causes of pain in patients with diabetes.