Hypertriglyceridemia impairs HDL functionality, promotes macrophage metabolic activation and exacerbates antigen-induced rheumatoid arthritis in mice which can be reversed by fenofibrate treatment.

Rheumatoid arthritis (RA) is associated with increased cardiovascular disease (CVD) risk, partly attributed to altered lipid metabolism. Apolipoprotein C-III (ApoC-III), a key regulator of triglyceride-rich lipoproteins in the plasma, has been implicated in both dyslipidemia and inflammation. In this study, we investigated the role of hypertriglyceridemia in RA using a transgenic mouse model overexpressing the human ApoC-III gene (ApoC-III Tg). Using a protocol of antigen-induced arthritis (AIA), we show that ApoC-III Tg mice exhibited significantly greater joint swelling, inflammatory infiltration and cartilage destruction compared to non-transgenic controls. These changes were accompanied by altered lipoprotein distribution in serum and High Density Lipoprotein (HDL) dysfunction including reduced antioxidant function. Furthermore, HDL isolated from arthritic ApoC-III Tg mice had pro-inflammatory properties on macrophages as demonstrated by the increased expression of iNOS and IL1β as well as increased mitochondrial respiration. Treatment of arthritic ApoC-III Tg mice with fenofibrate, a triglyceride-lowering drug, reduced triglyceride levels and increased ApoA-I content in HDL fractions. Importantly, fenofibrate significantly ameliorated arthritis severity, restored HDL antioxidant function and reduced macrophage activation. These findings highlight a mechanistic link between dyslipidemia, HDL dysfunction, and inflammatory exacerbation in RA and suggest that targeting ApoC-III-associated pathways may offer therapeutic benefit in patients with coexisting metabolic and inflammatory disorders.