Abstract
Irisin, a novel myokine secreted by skeletal muscle, promotes browning of white fat and influences glucose and energy homeostasis. Irisin and vitamin D are also known for their roles in the musculoskeletal system. In this study, we examined the impact of vitamin D correction on circulating irisin in Saudi subjects. For this, vitamin D deficient subjects (<= 50 nmol/l) were advised to receive adequate sunlight, eat vitamin D enriched foods and retain normal physical activity for correction/improvement in vitamin D status. Seventy-eight (30 male and 48 female) subjects, who responded to vitamin D intervention, were selected for further analyses. Anthropometry and routine biochemical assay were performed. Serum 25 (OH) D was analyzed using electrochemiluminiscence. Irisin levels were analyzed at baseline and after 12-month of intervention. Serum 25 (OH) D levels were significantly increased at post-intervention compared to baseline value (51.0 +/- 4.0 vs. 27.8 +/- 2.3 in males and 69.1 +/- 4.5 vs. 27.1 +/- 1.8 in females). With an increase in the levels of vitamin D adjusted for age and BMI, a corresponding increase in irisin level was observed in males (P=0.026) and to a lesser extent in females (P=0.093). Thus, vitamin D correction had a significant impact on irisin levels in male Saudi subjects but in females it failed to reach at significance. Further studies are needed in other ethnic population to better understand the influence of vitamin D on irisin regulation and secretion.