APOA1 and metabolic syndrome: The effect of PCSK1 on metabolic syndrome traits could be due to (1) its activity in energy metabolism, as mentioned above, (2) regulation of blood pressure by the renin–angiotensin–aldosterone system (RAAS), as PCSK1 is involved in the processing of prorenin to renin, and variants in this gene could affect the RAAS [47], or (3) the involvement of PCSK1 in glucose and lipid metabolism by modulating insulin and APOA1 production [48,49].