Habitual physical activity is associated with circulating irisin in healthy controls but not in subjects with diabetes mellitus type 2

Background: Irisin, a novel myokine, has been shown to increase following vigorous exercise, with studies suggesting that it mediates some of the beneficial effects of exercise. Irisin might play a role in 'browning' of white adipocytes, thus increasing energy expenditure. The role of irisin in exercise and energy expenditure in subjects with diabetes mellitus type 2 (DMT2) remains largely unknown. We aimed to investigate the association between circulating irisin and habitual physical activity in subjects with and without DMT2. Material and methods: In this cross-sectional study, 164 Saudi adults: 81 non-DMT2 controls [age: (mean Â+_ SD) 51.6 Â+_ 10.9; BMI: 29.6 Â+_) 4.3 kg/m2] and 83 DMT2 subjects [age: 54.3 Â+_ 10.3 year; BMI: 29.4 Â+_ 4.7 kg/m2] were studied. Anthropometric and fasting serum biochemical data were collected. Circulating irisin was measured using an enzyme-linked immunosorbent assay (ELISA). Frequency intensity time (FIT) index was used to assess the level of habitual physical activity. Results: We observed significantly higher levels of irisin in DMT2 subjects than in controls (P < 0.001). FIT index was positively associated (r = 0.20, P = 0.03) with circulating irisin in controls only. Additionally, irisin levels were significantly higher in tertile 3 (0.75 Â+_ 0.07 μg/mL) than tertile 1 (0.49 Â+_ 0.06 μg/mL) of the FIT index in healthy controls, whilst no such relation with physical activity was observed in DMT2 subjects. Conclusion: This cross-sectional study has shown a weak association of irisin with physical activity levels in healthy controls but not in DMT2 subjects, suggesting the possibility of discordant regulation in the condition of DMT2.