The Novel Apolipoprotein A5 Is Present in Human Serum, Is Associated with VLDL, HDL, and Chylomicrons, and Circulates at Very Low Concentrations Compared with

A5 (ApoA5) is fast gaining attention as a key regulator of serum triglyceride concentrations. An ApoA5 mouse knock-out model produced an approximately fourfold increase in serum triglycerides, whereas a knock-in model with human ApoA5 produced 50–70 % lower concentrations of mouse serum triglycerides. In addi-tion, peroxisome proliferator-activated receptor- ago-nists, which are used clinically to lower serum triglyc-eride concentrations, cause increased ApoA5 mRNA expression. Despite these compelling molecular biology data, relatively little is known about ApoA5 protein in human serum. Methods: To better understand circulating concentra-tions and lipoprotein particle distribution of ApoA5, we expressed the recombinant human ApoA5 protein an