ANGPTL8 R59W variant influences inflammation through modulating NF-κB pathway under TNFα stimulation

Background ANGPTL8 is known to regulate lipid metabolism and inflammation. It interacts with ANGPTL3 and ANGPTL4 to regulate LPL activity, and with IKKα/β to modulate NF-κB activity. Further, a SNP leading to ANGPTL8 R59W variant associates with reduced LDL/HDL and increased FBG in Hispanic and Arab individuals, respectively. In this study, we investigate the impact of R59W variant on the inflammatory activity of ANGPTL8. Methods ANGPTL8 R59W variant was genotyped in a discovery cohort of 867 Arab individuals from Kuwait. Plasma levels of ANGPTL8 and inflammatory markers were measured and tested for associations with the genotype; the associations were tested for replication in an independent cohort of 278 Arab individuals. Impact of the ANGPTL8 R59W variant on NF-κB activity was examined using approaches including overexpression, luciferase assay, and structural modeling of binding dynamics. Results The ANGPTL8 R59W variant was associated with increased circulatory levels of TNFα and IL7. NF-κB activity, as assessed by the increased in the phosphorylation of IKK-α/β protein, IκBα, and NF-κB p-65 in R59W variant compared to wild type, and TNFα stimulation further elevated it. This finding was substantiated by increased luciferase activity of NF-κB p65 with the R59W variant. Modeled structural and binding variation due to R59W change in ANGPTL8 agreed with the observed increase in NF-κB activity. Conclusion ANGPTL8 R59W is associated with increased circulatory TNFα, IL7 and NF-κB p65 activity. Weak transient binding of ANGPTL8 R59W variant explains its regulatory role on the NF-κB pathway and inflammation.