Characterization of the Metabolic Proteome of Serum From Patients With Diabetic Distal Symmetric Polyneuropathy

Aims: The pathophysiological of diabetic distal symmetric polyneuropathy (DSPN) remains to be elucidated and there are no diagnostic or prognostic biomarkers for the condition. In this explorative proteomic study, metabolic proteome profiling of serum in patients with/without DSPN was analyzed. We aimed to discover proteins with different abundance ranges through proximity extension assay (PEA) technology. Methods: Temperature quantitative sensory testing (QST) and electromyography (EMG) were used to access the small- and large-fiber function of all participants, respectively. The metabolic proteome profile of serum was analyzed using PEA technology (Olink Target 96 METABOLISM panel). Results: We evaluated serum from patients without DSPN (n = 27), with small-fiber neuropathy (SFN, n = 25) and with mixed small- and large-fiber neuropathy (MSLFN, n = 24). Fifteen proteins, which were especially related to immune response, insulin resistance, and lipid metabolism, were significantly different between patients without DSPN and with MSLFN. Besides, seven proteins, especially related to extracellular structure organization, were significantly different between serum from patients with SFN and with MSLFN. What's more, serum from patients without DSPN showed that three proteins, related to immune response, altered significantly compared to serum from patients with SFN. Conclusions: This was the first study that characterized the metabolic proteomic profile of serum in DSPN patients by analyzing a panel of 92 metabolic proteins using PEA technology.