Safarpour P, Daneshi-Maskooni M, Vafa M, et al. - In view of the possibility that vitamin D (VD) supplementation may improve the levels of sirtuin 1 (SIRT1) and subsequently PPAR-γ coactivator 1α and irisin, which in turn may decrease insulin resistance (IR), researchers here examined how VD supplementation affects SIRT1, irisin, and IR in overweight/obese type 2 diabetes (T2D) patients. They conducted a clinical trial study recruiting 90 T2D males and females (mean of age and BMI of intervention and placebo groups were 50.05 ± 10.17 and 50.36 ± 10.2 yrs. and 31.37 ± 3.4 and 30.43 ± 3.2 kg/m², respectively). The inclusion criteria were T2D, VD deficient, BMI > 25 kg/m2, and serum HbA1c < 8.5%. For 8 weeks, 50,000 IU/week VD or placebo was provided to the participants. The intervention group exhibited a significant increase in serum VD, SIRT1, and irisin and showed a significant decrease in HbA1c by 1%.