Objective To investigate the dynamic changes of serum regulatory T cell (Treg cell)-related factors in patients with diabetic peripheral neuropathy (DPN) and their relationships with pain mediators.

Methods A total of 140 patients with DPN were enrolled and divided into painful DPN group (36 patients) and painless DPN group (104 patients) based on the presence of neuropathic pain. The serum levels of Treg cell-related factors interleukin-10 (IL-10), transforming growth factor-β1 (TGF-β1), interleukin-35 (IL-35) and pain mediators prostaglandin E2 (PGE2), histamine (His), and 5-hydroxytryptamine (5-HT) between the two groups were compared. Pearson correlation analysis was used to explore the correlations of the serum levels of IL-10, TGF-β1, and IL-35 with the levels of PGE2, His, and 5-HT in patients with DPN. Multiple linear regression analysis was conducted to investigate the influencing factors of pain intensity in patients with DPN.

Results The serum levels of TGF-β1, PGE2, His, and 5-HT were higher, while the levels of IL-10 and IL-35 were lower in the painful DPN group than those in the painless DPN group(P < 0.05). Pearson correlation analysis showed that IL-10 was negatively correlated with PGE2, His, and 5-HT (r=-0.781, -0.794, -0.714, P < 0.05); TGF-β1 was positively correlated with PGE2, His, and 5-HT (r=0.605, 0.590, 0.515, P < 0.05); IL-35 was negatively correlated with PGE2, His, and 5-HT (r=-0.727, -0.847, -0.727, P < 0.05). Multiple linear regression analysis revealed that IL-10, TGF-β1, and IL-35 were closely related to the pain intensity in patients with DPN and were influencing factors of painintensity (P < 0.05).

Conclusions The serum levels of IL-10 and IL-35 in patients with DPN are negatively correlated with the levels of PGE2, His, and 5-HT, while the level of TGF-β1 is positively correlated with these pain mediators. Furthermore, IL-10, TGF-β1, and IL-35 are closely related to the degree of neuropathic pain in patients with DPN.