Background: ANGPTL8 has been recently identified as lipid metabolism and inflammation regulator. It interacts with ANGPTL3 and, more recently, ANGPTL4 to regulate LPL activity. It was also shown to modulate NF-κB activity through its interaction with ikkα/β. A genetic variant rs2278426 (R59W) in ANGPTL8 has been associated with reduced LDL and HDL in Hispanics and increased FBG in Arabs. The objective of the study was to investigate the impact of the R59W variant on LPL and the inflammatory activity of ANGPTL8.
Methods: ANGPTL8 was genotyped in a discovery cohort of 738 Kuwaiti individuals. ANGPTL8 level, as well as inflammatory markers and LPL, were measured in plasma. Additionally, metabolite analysis, overexpression, luciferase binding assay, confocal microscopy, and cellular fractionation analyses were conducted in the HepG2 cell line to assess differences between the ANGPTL8 and its variant.
Results: The ANGPTL8 rs2278426 variant was associated with an increase in circulatory levels of TNF-α and IL7 in our cohort. Carrier versus reference genotype of the studied variant showed differences in the following metabolites: Acylcarnitines, Phosphatidylcholine, and Cholesteryl Ester. These metabolites are implicated in modulating NF-κB and TNF-α levels. Our in vitro analyses showed that the activity levels of NF-κB p65 was higher in the R59W than the wild type, and it was further elevated with TNFα stimulations. The data was validated by the luciferase activity, confocal microscopy, and cellular fractionation.
Conclusion: This study showed that ANGPTL8 variant R59W is associated with increased circulatory TNF-α and IL7 levels but not the LPL plasma levels. We have also demonstrated the pro-inflammatory role of the R59W variant in regulating the NF-κB pathway as reflected by genotyping, in vitro, metabolomics, and structural analyses. Further studies are needed to expand our understanding of other signaling pathways and possible crosstalk in the context of inflammation.
A.Mohammad: None. A.T.Thangavel: None. F.Almulla: None. J.Abubaker: None. M.Abu-farha: None. D.Madhu: None. P.T.Cherian: None. I.Al khairi: None. P.Hebbar: None. S.A.Kavalakatt: None. H.Arefanian: None. N.Alam-eldin: None.
Kuwait Foundation for the Advancement of Sciences