Association between Serum Irisin Levels and Non-Alcoholic Fatty Liver Disease in Health Screen Examinees

Irisin is a recently found myokine that aids obesity control and improves glucose homeostasis by acting on white adipose tissue cells and increases total energy consumption. The aim of this study was to evaluate serum irisin levels in patients with non-alcoholic fatty liver disease (NAFLD) and to compare these levels with those of normal controls. Among 595 health screen examinees who had visited our institute between January 2013 to March 2013, 355 patients (84 NAFLD patients and 271 normal controls) were enrolled depending on whether they gave written informed consents and their history of alcohol intake, blood tests, and abdominal ultrasonographic findings. Age; sex; laboratory test parameters; homeostasis model assessment-insulin resistance; and levels of leptin, adiponectin, and irisin were assessed. Serum irisin levels (ng/ml) were significantly higher in the NAFLD group than in normal controls (63.4 ± 32.6 vs. 43.0 ± 29.7, p<0.001) and higher in the mild fatty liver group than in the moderate-to-severe fatty liver group (68.3 ± 38.2 vs. 56.6 ± 21.2, p<0.001). Additionally, serum irisin levels were not different between the non-obese and obese groups (48.4 ± 34.2 vs. 45.8 ± 22.9, p = 0.492); however, the levels were significantly lowest in normal controls and highest in the mild fatty liver group in the non-obese (44.9 ± 31.7 vs. 73.1 ± 48.5 vs 59.7 ± 18.0, p<0.001) and obese groups (35.0 ± 17.0 vs. 62.9 ± 21.2 vs. 54.6 ± 23.3, p<0.001). Serum irisin levels were significantly higher in NAFLD patients, which is not consistent with the results of previously published studies. Therefore, more studies are needed to confirm the role of irisin in NAFLD.