FNDC5 and metabolic syndrome: Figure 1B shows that with increasing numbers of MetS components, the serum level of irisin also increased (the ratios ± SD for 0–2 components vs. 3 components vs. 4–5 components were 6.59 ± 3.28 vs. 7.23 ± 3.57 vs. 9.16 ± 3.79, P = .008 between group 0–2 and group 4–5).