The association of vitamin D with inflammatory cytokines in diabetic peripheral neuropathy.

[Purpose] The effects of vitamin D on the circulating levels of IL-17 and IL-13 were investigated in patients with diabetic peripheral neuropathy, patients with diabetes mellitus type 2 without neuropathy, and healthy controls. [Subjects and Methods] A single-blind controlled clinical study was performed, including70 type 2 diabetic patients with or without diabetic peripheral neuropathy and 33 healthy volunteer controls. The 25(OH)D levels were evaluated using ultra-performance liquid chromatography, and IL-17 and IL-13 levels were assessed using enzyme-linked immunosorbent assays. [Results] The 25(OH) vitamin D concentration was lower in diabetic peripheral neuropathy patients than in diabetes mellitus patients without neuropathy and healthy controls. Similarly, 25(OH)D levels were lower in diabetes mellitus patients than healthy controls. IL-17 and IL-13 levels were higher in diabetes mellitus patients than in controls. Additionally, IL-13 levels were higher in diabetic peripheral neuropathy patients than in diabetes mellitus patients without neuropathy. These differences were statistically significant. There was a significant positive correlation between 25(OH)D and IL-13,and a negative correlation between 25(OH)D andIL-17 in the diabetic and diabetic neuropathy groups. [Conclusion] Vitamin D is a potential modifiable risk factor for diabetic peripheral neuropathy and may regulate inflammatory mediators, e.g., IL-17 and IL-13.