A single blinded randomized controlled trial assessing the effect of photobiomodulation therapy on neuron specific biomarkers in type II diabetes mellitus patients with peripheral neuropathy

Background: Diabetic peripheral neuropathy is one of the most devastating complications of long-term diabetes mellitus, associated with functional limitations and poor quality of life. Materials and methods: Two hundred subjects were randomized into intervention and control group, with one hundred in each arm. The intervention arm received photobiomodulation therapy for ten days, with Low −Level Helium-Neon Laser at a wavelength of 632.8 nm of dosage 3.1 J/cm² for 9 min on both the dorsal and plantar surfaces of the foot, while the control group received sham laser. Patients were assessed at day 0 of treatment and four weeks after treatment for all the clinical and neuropathy-specific biomarkers. Serum levels of Neuron specific enolase (NSE), Calcitonin gene related peptide (CGRP) Nerve Growth Factor (NGF) for monitoring neuronal changes and monofilament test, Biothesiometer, Numeric Pain Rating Scale (NPRS) to analyze vibration sensation, and pain score. The neuropathic quality of life was assessed using the Norfolk Quality of Life Questionnaire- Diabetic Neuropathy (Norfolk QOL-DN). Result: Trial found significant changes in serum NSE (p < 0.001), CGRP(p < 0.001), MNSI(p < 0.001), VPT(p < 0.001), NPRS(p < 0.001), and NQL(p < 0.001) in the intervention group four weeks after receiving photobiomodulation therapy, whereas no changes in NGF levels(p = 0.937). This was in correlation with improved neuropathic pain and quality of life. Conclusion: Serum levels of NSE and CGRP may be good indicators of effectiveness of photobiomodulation in reducing neuropathic pain and other symptoms in individuals with DPN. Reduced neuropathic symptoms, improved protective sensation of foot and quality of life, and reduced neuropathic pain was observed in intervention group.