Biomarkers for the Development and Progression of Diabetic Polyneuropathy

Objective. To study the diagnostic significance of brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGFA) and their high-affinity receptors (TrkB, VEGFR2) in relation to the development and progression of diabetic polyneuropathy. Materials and methods. The study group included 65 patients with diabetes mellitus and confirmed diabetic polyneuropathy. The reference group consisted of 14 patients with diabetes mellitus without diabetic polyneuropathy. The control group consisted of 15 presumptively healthy subjects. The clinical parameters of polyneuropathy were evaluated on the PainDetect VAS, the Total Symptom Score (TSS), the neurological Symptom Score (NSS), and the Neuropathy Disability Score (NDS). The severity of polyneuropathy was verified by electoneuromyography of the lower limbs. Serum growth factor concentrations and the concentrations of their receptors were study by immunoenzyme analysis. Results. Serum from patients with diabetic polyneuropathy, independently of the presence of clinical symptomatology, showed increases in BDNF, VEGFA, and TrkB. The severe stage of diabetic polyneuropathy was characterized by painless symptomatology, with deficiency of serum BDNF, VEGFA, and VEGFR2, but high levels of TrkB. The BDNF level affected the intensity of neuropathic pain and the clinical signs of diabetic polyneuropathy and was linked with the severity of axon damage to sensory nerve fibers. Increased TrkB was associated with the painless form of neuropathy and the extent of nerve fiber demyelination. Conclusions. Increases in the serum expression of BDNF and VEGFA have been been proposed as a marker for the development of diabetic polyneuropathy, while different concentrations of TrkB and VEGFR2 receptors can be regarded as predictors of severe course of disease.