ApoA5 (Apolipoprotein A5) is  a key regulator of serum triglyceride concentrations. An ApoA5 mouse knock-out model produced an approximately four fold increase in serum triglycerides, whereas a knock-in model with human ApoA5 produced 5070% lower concentrations of mouse serum triglycerides. In addition, peroxisome proliferator-activated receptor-agonists, which are used clinically to lower serum triglyceride concentrations, cause increased ApoA5 mRNA expression. ApoA5 is present in human serum detected by polyclonal antibodies against both the NH2 and COOH termini, although at much lower concentration than other apolipoproteins.