A study published in the current issue of Psychotherapy and Psychosomatic has identified a biomarker for depression in diabetes. Findings of epidemiological studies have shown an overall 2-fold increased prevalence of depression in patients with type 2 diabetes compared with the general population worldwide. Consequently, identifying biological markers and potential therapeutic targets for depression intervention seems crucial to effectively manage comorbid depression in patients with diabetes and improve health outcomes.
Dipeptidyl peptidase-4 (DPP4) is a widely expressed multifunctional exopeptidase that exists as a membrane-anchored cell surface protein or in a soluble form in the plasma. DPP4 inhibitors have already been widely used as novel antidiabetic drugs in clinical practice; however, no study has ever evaluated the association between DPP4 activity and depression in type 2 diabetes. data indicated that the risk of depression increased significantly with higher levels of HbA1c, IL-6, CPR, nitrotyrosine, and 8-iso-PGF2a. In addition, increased plasma DPP4 activity has been proved to promote the development of hyperglycemia and to enhance inflammatory response and increase reactive oxygen species generation.
This study included cross-sectional data from a total of 1,458 type 2 diabetic patients aged between 40 and 82 years. Results support a positive association between hyperglycemia, inflammation, oxidative stress and DPP4 activity in type 2 diabetes. Moreover, the risk of depression got more pronounced among patients with rising DPP4 activity and higher levels of HbA1c, IL-6, CRP, nitrotyrosine, and 8-iso-PGF2a. Taken together these findings suggest that since DPP4 may be a pathogenic factor for hyperglycemia, inflammation and oxidative stress, it could promote depression development through these 3 pathways.