Use of a proximity extension proteomics assay to discover novel biomarkers associated with circulating leptin levels in two populations with type 2 diabetics

Abstract Background We used a multiplex proteomics assay with the aim to discover novel associations between leptin and 88 circulating proteins in order to provide additional insights into the role of leptin in the development of CVD in patients with type 2 diabetes (T2DM). Material and methods In a discovery phase, we investigated associations between 88 plasma proteins, assessed with a proximity extension assay, and plasma leptin in a cohort of middle-aged patients with T2DM (CARDIPP, n=661). Associations that passed the significance threshold of a False discovery rate of 5% (corresponding to p <0.0017) were replicated in diabetes patients in an independent cohort (PIVUS, n=116). We also investigated if proteins mediated the longitudinal association between plasma leptin and the incidence of major cardiovascular events (MACE). Results Two proteins were significantly associated with leptin in the discovery phase, adipocyte fatty acid binding protein (A-FABP) (regression coefficient .118, 95% CI (.064, .173) p =0.000024) and adrenomedullin ( p =0.000002) but only A-FABP was significantly associated with leptin in the replication cohort (regression coefficient .0254, 95% CI (.119, .39) p =0.0003). Multiplicative interaction analyses in the two cohorts suggest a stronger association between A-FABP and leptin in men than in women. In longitudinal analyses, the association between leptin and MACE was slightly attenuated after adding A-FABP to the multivariate model. Conclusions Our analysis identified a consistent association between leptin and A-FABP in two independent cohorts of patients with T2DM, particularly in men. Our data encourage future large-scale proteomics analyses for additional insights into leptin biology.