Apolipoprotein A-IV of diabetic-foot patients upregulates tumor necrosis factor alpha expression in microfluidic arterial models

Diabetic peripheral arterial atherosclerosis is one of the important characteristics of diabetic foot syndrome. Apolipoprotein (Apo A-IV) participates in various physiological processes, and animal studies have shown that it has roles of anti-atherosclerosis, prevention of platelet aggregation and thrombosis. Apo A-IV glycosylation is closely related to the occurrence and development of diabetic peripheral atherosclerosis. This study aimed to explore the mechanism of diabetic peripheral arterial lesions caused by glycosylated Apo A-IV. Type 2 diabetes mellitus (T2DM) and T2DM with diabetic foot patients (T2DM-F; n = 45, 30) were enrolled in this study, and individuals without diabetes (n = 35) served as normal controls (NC). In T2DM group, serum Apo A-IV content was higher than those in NC and T2DM-F group, as carboxymethyl lysine (CML) glycosylation of Apo A-IV in mixed serum from T2DM-F group was identified to be more significant than those in two other groups. Within a microfluidic arterial chip model, Apo A-IV from T2DM and T2DM-F group significantly increased transcription and protein levels of tumor necrosis factor alpha (TNF-alpha) in chip arteries, and CML expression was observed in T2DM-F group, which were associated with increased nuclear receptor subfamily 4 group A member 3 (NR4A3) expression. Recombinant human Apo A-IV could reverse the stimulating effect of serum Apo A-IV from T2DM-F group on TNF-alpha expression, and NR4A3 blocking peptide downregulated TNF-alpha expression by inhibiting NR4A3 expression. In the chip arteries, Apo A-IV from T2DM and T2DM-F increased TNF-alpha expression and turn them into a pre-atherosclerotic state, which might be one of the important mechanisms of glycosylated Apo A-IV to induce diabetic peripheral arterial lesions and eventually lead to diabetic foot.