Modulation of Interleukin-8 Production by Vitamin D Supplementation in Indonesian Patients with Diabetic Polyneuropathy: A Randomized Clinical Trial

OBJECTIVES: We sought to assess the modulation of interleukin-8 (IL-8) production by vitamin D supplementation in Indonesian patients with diabetic polyneuropathy (DPN). METHODS: We conducted a cohort prospective, randomized, placebo-controlled, double-blind trial. This study was approved by the Local Ethical Committee and conducted from July 2018 to February 2019. We recruited 50 subjects with type 2 diabetes mellitus attending Haji Adam Malik General Hospital Medan, and divided them into two groups. The groups were treated for 10 weeks, either with placebo or vitamin D (D(3)) supplementation of 50 000 IU/week. They were evaluated by routine nerve conduction study (NCS) in the upper and lower limbs, and their serum vitamin 25-hydroxyvitamin D (25(OH)D) and IL-8 levels before and 10 weeks after placebo or vitamin D supplementation were measured. The role of IL-8 and vitamin D supplementation on the NCS was analyzed using linear regression. RESULTS: There was a significant difference between the mean vitamin 25(OH)D (p = 0.001) and IL-8 levels (p = 0.002) before and after vitamin D supplementation. There was no significant correlation between changes in vitamin 25(OH)D and IL-8 levels (p = 0.743). There was significant role of IL-8 on amplitude of the sensory sural nerve (p = 0.047; B = -0.009) and the nerve conduction velocity (NCV) of the motor tibial nerve (p = 0.007; B = -0.027). There was a significant role of vitamin D supplementation on NCSs. CONCLUSIONS: Higher IL-8 levels were correlated with poorer amplitude of the sensory sural nerve and the NCV of motor tibial nerves. Lower vitamin 25(OH)D levels were correlated with poorer distal latencies, amplitudes, and NCVs. There was no significant correlation between vitamin 25(OH)D and IL-8 levels. Thus, no sufficient evidence that vitamin D supplementation modulates IL–8 in Indonesian patients with DPN. Vitamin D(3) improved NCSs in diabetic patients.