Modulation of Brown Adipose Tissue Activity by HIIT and Vitamin D₃ Supplementation in Type 2 Diabetes Rat Models

Abstract Background Type 2 diabetes mellitus (T2DM) is a chronic disorder marked by hyperglycemia from insulin resistance and impaired secretion. Because adipose tissue regulates energy and glucose, activating brown adipose tissue (BAT) may offer therapeutic benefit. High-intensity exercise improves metabolic health, and low vitamin D is linked to worse insulin function and higher T2DM risk. Hence, the aim of the current study was to investigate the impact of high-intensity interval training (HIIT) and vitamin D₃ supplementation on BAT in T2DM rats. Methods and Results Forty male Wistar rats (6–8 weeks old, ~ 220 g) were used to induce T2DM via a high-fat diet (HFD) and Streptozotocin (STZ). Rats were randomized into five groups (n = 8 each): healthy control (HC), diabetic control (DC), diabetic HIIT (DT), diabetic vitamin D₃ (DV), and diabetic HIIT plus vitamin D₃ (DTV). Interventions lasted 8 weeks, with HIIT performed on a treadmill (5 days/week) and vitamin D₃ administered by weekly subcutaneous injection (10,000 IU/kg). Western blotting was used to assess protein changes related to the interventions. This study shows that eight weeks of HIIT combined with vitamin D₃ supplementation significantly enhanced the expression of FGF21, GPR120, PGC-1α, and UCP1 in BAT of T2DM rats. Vitamin D₃ alone elevated all four proteins, while HIIT alone increased only GPR120 and UCP1. Conclusion These results suggest vitamin D₃ as a potential means to enhance BAT activity in type 2 diabetes, highlighting its value as a non-pharmacological approach to improving metabolic control.