Serum irisin level, which has been significantly downregulated in type 2 diabetes patients [21–23], was associated with major adverse cardiovascular events in patients with established coronary artery disease after percutaneous coronary interventions [24], conferred with prognostic value for MetS and fasting plasma glucose in Chinese abdominally obese adults [25], and validated as an independent predictor for the severity of coronary artery disease in patients with stable angina [26]. This evidence concerns the gene FNDC5 and metabolic syndrome.