Immune Metabolic Associations in Psoriatic Arthritis

Psoriatic arthritis (PsA) and psoriasis are characterised by immune, metabolic, and vascular dysfunction. There is an increase in Major Adverse Cardiovascular Events in people with PsA and psoriasis not explained by conventional cardiovascular risk factors. Furthermore, obesity in psoriasis is associated with increased risk of developing PsA3. Dietary interventions leading to weight loss \>5% are associated with a higher rate of achievement of minimal disease activity in overweight/obese patients with PsA treated with TNF inhibitors. Phosphodiesterase 4 (PDE4) inhibition with apremilast is licensed for the treatment of PsA and psoriasis and has been noted to be associated with weight loss. There is also data from animal models to suggest a role for PDE4 in glucose metabolism. However, the exact mechanisms underlying this are unclear and warrant investigation in humans. PDE4 may help explain the link between the immune and cardiometabolic dysfunction that characterises PsA and psoriasis, with pathogenic and therapeutic implications. This study aims to use apremilast as a clinical molecular probe to evaluate the effects of PDE4 inhibition on metabolic, vascular, and immune status in patients with PsA and psoriasis. The hypothesis is that PDE4 inhibition mediates profound and synergistic effects on immune and metabolic pathways in these conditions to improve metabolic status and normalise dysregulated immunity. Measurement of metabolic, immunological and vascular outcomes in 60 patients (40 with PsA and 20 with psoriasis) receiving apremilast as part of their standard clinical care will be taken. A subgroup of 20 participants with PsA will also undergo more in-depth investigations including MRI of abdominal fat, subcutaneous fat biopsy, measurement of vascular endothelial function using EndoPAT and more detailed deep-immunophenotyping. Patients will be recruited from rheumatology and dermatology clinics in NHS Greater Glasgow and Clyde (primary site) and two other recruiting sites in Scotland via the Scottish Collaborative Arthritis Research network (SCAR).