Association between serum neopterin level and diabetic peripheral neuropathy in patients with type 2 diabetes: a pilot observational study.

Background: Diabetic peripheral neuropathy (DPN) is a prevalent and disabling complication of type 2 diabetes mellitus (T2D), leading to significant morbidity and reduced quality of life. Chronic hyperglycemia, metabolic disturbances, and immune system activation are contributors to the development and evolution of DPN. Neopterin, a pteridine derivative produced by activated macrophages, reflects cellular immune activation and oxidative stress, both of which are implicated in diabetic complications. However, the role of serum neopterin as a potential biomarker for diabetic neuropathy has not been fully elucidated. This study aimed to investigate the association between serum neopterin levels and diabetic peripheral neuropathy in patients with T2D. Methods: A total of 90 participants were enrolled, including 60 patients with T2D and 30 age- and sex-matched healthy controls. The T2D group was subdivided into 30 patients with DPN and 30 patients without DPN. Serum neopterin levels were measured using ELISA. All participants underwent nerve conduction studies (NCS) and Toronto clinical neuropathy score (TCNS) assessments. Glycemic and lipid profiles were also analyzed. Results: Serum neopterin levels were significantly elevated in T2D patients with DPN compared to those without neuropathy and healthy controls. Higher neopterin levels were strongly associated with neuropathy severity, as patients with axonal neuropathy exhibited the highest neopterin concentrations. Additionally, neopterin correlated positively with TCNS scores, NCS results, and altered lipid profile, suggesting a link between metabolic dysregulation and immune activation in DPN. Conclusion: Elevated serum neopterin levels may reflect underlying immune activation and oxidative stress in T2D patients with DPN. Neopterin could function as a valuable biomarker for the early detection and severity assessment of DPN.