INS and metabolic syndrome: Moreover, although direct correlations between FGF-21 levels and triglycerides (TG), glycemia, lipids, and insulin levels have been shown (12), the role of FGF-21 in obesity, diabetes, non-alcoholic fatty liver disease (NAFLD), Metabolic Syndrome (MetS), and coronary artery disease (CAD) is still debated (13–15).