An APOA5 3′ UTR Variant Associated with Plasma Triglycerides Triggers APOA5 Downregulation by Creating a Functional miR-485-5p Binding Site

APOA5 c.∗158C>T (rs2266788), located in the 3′ UTR, belongs to APOA5 haplotype 2 (APOA5∗2), which is strongly associated with plasma triglyceride levels and modulates the occurrence of both moderate and severe hypertriglyceridemia. Individuals with APOA5∗2 display reduced APOA5 expression at the posttranscriptional level. However, the functionality of this haplotype remains unclear. We hypothesized that the hypertriglyceridemic effects of APOA5∗2 could involve miRNA regulation in the APOA5 3′ UTR. Bioinformatic studies have identified the creation of a potential miRNA binding site for liver-expressed miR-485-5p (MIRN485-5p) in the mutant APOA5 3′ UTR with the c.∗158C allele. In human embryonic kidney 293T (HEK293T) cells cotransfected with an APOA5 3′ UTR luciferase reporter vector and a miR485-5p precursor, c.∗158C allele expression was significantly decreased. Moreover, in HuH-7 cells endogenously expressing miR-485-5p, we observed that luciferase activity was significantly lower in the presence of the c.∗158C allele than in the presence of the c.∗158T allele, which was completely reversed by a miR-485-5p inhibitor. We demonstrated that the rare c.∗158C APOA5 allele creates a functional target site for liver-expressed miR-485-5p. Therefore, we propose that the well-documented hypertriglyceridemic effect of APOA5∗2 involves an APOA5 posttranscriptional downregulation mediated by miR-485-5p.