APOB and metabolic syndrome: With the increased research on serum lipids, the lipoprotein fraction of apolipoprotein AI (Apo AI) and apolipoprotein B (Apo B) and the ratios of apolipoprotein B/apolipoprotein AI (Apo B/Apo AI), and lipoprotein(a) [Lp(a)] have received considerable attention in investigating dyslipidemia-related diseases in recent years; Apo B/Apo AI and Lp(a) were recognized as the independent risk factors for various diseases, including osteoarthritis and AS [19–21].