Dipeptidyl-peptidase 4 and attractin expression is increased in circulating blood monocytes of obese human subjects

Dipeptidyl-peptidase (DPP)-4, which catalizes the degradation of the insulinotropic incretin glucagon-like-peptide (GLP)-1, and the DPP-4 like enzyme attractin are involved in activation of T-lymphocytes and monocytes. Recently, it has been demonstrated, that the risk for certain infections is increased in type 2 diabetic patients under DPP-4 inhibitor treatment. The aim of the present study was to examine the expression of DPP-4 and attractin in circulating blood monocytes of obese and type 2 diabetic subjects. Monocytes were isolated by CD14-antibody based magnetic cell sorting from blood samples of 17 lean controls, 20 obese, non-diabetic subjects and 19 obese patients with type 2 diabetes. FACS analysis was performed to test purity of the cell preparations. Expression was measured by multiplex RT-PCR on RNA-level. DPP-4 and attractin were detectable in human circulating monocytes with attractin being expressed at higher levels compared to DPP-4. Both enzymes were significantly higher expressed in circulating blood monocytes of obese subjects compared to lean controls. In contrast, type 2 diabetes did not significantly affect expression levels. Finally, neither DPP-4 nor attractin expression was altered by sitagliptin or insulin treatment. In conclusion, our data demonstrate, that expressions of DPP-4 and attractin in circulating blood monocytes of human subjects are influenced by metabolic abnormalities with obesity being an important factor.