P20 - Phase-dependent effects of vitamin D on oxidative and immune pathways in a rat model of diabetes mellitus

Background/Introduction Oxidative stress and immune imbalance play central roles in diabetes mellitus. Existing literature demonstrates the influence of vitamin D on antioxidant and inflammatory pathways; however, its differential effects based on timing remain insufficiently understood. This study examined the distinct preventive and therapeutic roles of vitamin D on catalase (CAT), superoxide dismutase (SOD), interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) in a streptozotocin (STZ)-induced diabetic rat model. Purpose This study aimed to investigate preventive and therapeutic effects of vitamin D on CAT, SOD, IL-6 and TNF-α in an STZ-induced diabetes mellitus (DM) rat model. Methods Forty male rats (10 weeks old, ∼200 g) were divided into four groups: Group I – Intact controls; Group II – Diabetic rats (STZ only); Group III – Preventive group (vitamin D daily for 14 days before STZ); Group IV – Therapeutic group (vitamin D from day 3 post-STZ). DM was induced by a single intraperitoneal STZ dose (30 mg/kg). Vitamin D was given orally at 300 IU/day for 21 days. Blood samples were collected on days 7, 14 and 21 to assess CAT, SOD, IL-6 and TNF-α. The study was approved by the Ethics Committee of Tbilisi State Medical University (protocol #60-1002, dated 10.02.2023) and conducted in accordance with UFAW guidelines to ensure high standards of animal welfare. Results STZ-induced DM caused a progressive decline in antioxidant enzyme activity and cytokine levels. In the preventive group (III), vitamin D administration led to an early peak in CAT activity (day 14) and maintained moderate levels of IL-6 and TNF- α, suggesting potential protection against oxidative stress and immune suppression. In the therapeutic group (IV), vitamin D was associated with a gradual increase in SOD and CAT activities, along with higher cytokine levels by day 21. These patterns emphasize the timing-dependent biological effects of vitamin D. Conclusion(s) Vitamin D exerts preventive and therapeutic antioxidant and immunomodulatory effects in STZ-induced DM. Early use enhances antioxidant defenses and attenuates immune decline, while later use promotes recovery of antioxidant capacity and reactivation of cytokine signaling. These findings support the dual-phase potential of vitamin D in managing oxidative and inflammatory diabetic pathology.